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1.
Dong-Kyou Lee Dong-Hyun Cha Chun-Sil Jin Suk-Jin Choi 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(5):655-664
In this study, regional climate changes for seventy years (1980–2049) over East Asia and the Korean Peninsula are investigated using the Special Reports on Emission Scenarios (SRES) B1 scenario via a high-resolution regional climate model, and the impact of global warming on extreme climate events over the study area is investigated. According to future climate predictions for East Asia, the annual mean surface air temperature increases by 1.8°C and precipitation decreases by 0.2 mm day?1 (2030–2049). The maximum wind intensity of tropical cyclones increases in the high wind categories, and the intra-seasonal variation of tropical cyclone occurrence changes in the western North Pacific. The predicted increase in surface air temperature results from increased longwave radiations at the surface. The predicted decrease in precipitation is caused primarily by northward shift of the monsoon rain-band due to the intensified subtropical high. In the nested higher-resolution (20 km) simulation over the Korean Peninsula, annual mean surface air temperature increases by 1.5°C and annual mean precipitation decreases by 0.2 mm day?1. Future surface air temperature over the Korean Peninsula increases in all seasons due to surface temperature warming, which leads to changes in the length of the four seasons. Future total precipitation over the Korean Peninsula is decreased, but the intensity and occurrence of heavy precipitation events increases. The regional climate changes information from this study can be used as a fruitful reference in climate change studies over East Asia and the Korean peninsula. 相似文献
2.
Influence of vegetation changes during the Last Glacial Maximum using the BMRC atmospheric general circulation model 总被引:3,自引:0,他引:3
The influence of different vegetation distributions on the atmospheric circulation during the Last Glacial Maximum (LGM,
21 000 years before present) is investigated. The atmospheric general circulation model of the Bureau of Meteorology Research
Center was run using a modern vegetation and in a second experiment with a vegetation reconstruction for the LGM. It is found
that a change from conifer to desert and tundra causes an additional LGM cooling of 1–2 °C in Western Europe, up to −4 °C
in North America and −6 °C in Siberia. An expansion of dryland vegetation causes an additional annual cooling of 1–2 °C for
Australia and northern Africa. On the other hand, an increase of temperature (2 °C) is found in Alaska due to changes in circulation.
In the equatorial region the LGM vegetation leads to an increased modelled temperature of 0.5–1.5 °C and decreased precipitation
(30%) over land due to a reduction of the tropical rainforest, mainly in Indonesia, where the reduction of precipitation over
land is associated with an increase of precipitation of 30% over the western Pacific.
Received: 15 December 1999 / Accepted: 10 January 2001 相似文献
3.
Recent trends in observed temperature and precipitation extremes in the Yangtze River basin,China 总被引:14,自引:1,他引:14
Summary The present study is an analysis of the observed extreme temperature and precipitation trends over Yangtze from 1960 to 2002
on the basis of the daily data from 108 meteorological stations. The intention is to identify whether or not the frequency
or intensity of extreme events has increased with climate warming over Yangtze River basin in the last 40 years. Both the
Mann-Kendall (MK) trend test and simple linear regression were utilized to detect monotonic trends in annual and seasonal
extremes.
Trend tests reveal that the annual and seasonal mean maximum and minimum temperature trend is characterized by a positive
trend and that the strongest trend is found in the winter mean minimum in the Yangtze. However, the observed significant trend
on the upper Yangtze reaches is less than that found on the middle and lower Yangtze reaches and for the mean maximum is much
less than that of the mean minimum. From the basin-wide point of view, significant increasing trends are observed in 1-day
extreme temperature in summer and winter minimum, but there is no significant trend for 1-day maximum temperature. Moreover,
the number of cold days ≤0 °C and ≤10 °C shows significant decrease, while the number of hot days (daily value ≥35 °C) shows
only a minor decrease. The upward trends found in the winter minimum temperature in both the mean and the extreme value provide
evidence of the warming-up of winter and of the weakening of temperature extremes in the Yangtze in last few decades.
The monsoon climate implies that precipitation amount peaks in summer as does the occurrence of heavy rainfall events. While
the trend test has revealed a significant trend in summer rainfall, no statistically significant change was observed in heavy
rain intensity. The 1-day, 3-day and 7-day extremes show only a minor increase from a basin-wide point of view. However, a
significant positive trend was found for the number of rainstorm days (daily rainfall ≥50 mm). The increase of rainstorm frequency,
rather than intensity, on the middle and lower reaches contributes most to the positive trend in summer precipitation in the
Yangtze. 相似文献
4.
Raphael E. Okoola 《Meteorology and Atmospheric Physics》2000,73(3-4):177-187
Summary Climatological statistics of extreme temperature events over Kenya are established from the analysis of daily and monthly
maximum temperatures for a representative station (Nairobi Dagoretti Corner) over the period 1956–1997.
The months of June to August were shown to be the coldest with a mean monthly maximum temperature of less than 22 °C. Seasonal
(June to August) mean maximum temperature was 21.5 °C. Using this seasonal mean temperature for the period 1967–1997 delineated
1968 as the coldest year in this series and 1983 as the warmest year.
Spectral analysis of the seasonal data, for both the coldest and the warmest years, revealed that the major periods were the
quasi-biweekly (10 days) and the Intraseasonal Oscillations (23 days). Secondary peaks occurred at periods of 4–6 and 2.5–3.5
days.
A temperature threshold of 16.7 °C during July was used to define cold air outbreaks over Nairobi. This threshold temperature
of 16.7 °C was obtained from the mean July maximum temperature (20.9 °C) minus two standard deviations. Notable trends include
a decrease in the frequency of station-days, between 1956 and 1997, with temperatures less than 16.7 °C during July.
Surface pressure patterns indicate that the origin of the cold air is near latitude 25° S and to the east of mainland South
Africa. The cold air near 25° S is advected northwards ahead of the surface pressure ridge.
Received July 19, 1999 Revised January 11, 2000 相似文献
5.
On Climate Variations and Changes Observed in South Korea 总被引:1,自引:0,他引:1
This study describes observations on possible climate changes occurring on the Korean Peninsula. We found that in large urban and industrial areas in Korea, there has been a significant increase in the annual mean temperatures according to data of the past 29 years. The increase in January temperatures was in the order of 0.8 ~ 2.4 ° C. However, in rural and marine stations, the increase in annual mean temperature was 0.6 ° C; the level of the global average. There was also an increase in precipitation: 259 mm over the recent 97 years. Observation has revealed that a month-long steady rainfall in late June and July with a quasi-stationary polar front has not occurred in recent years and has been replaced with scattered convective heavy-showers on a local scale in July and August. It is observed that the behaviour of this rainy front, `the Changma front' has brought changes to rainfall characteristics. Our results highlight the importance of the shortened rainy season. However, the amount of rainfall and the number of heavy rainfall days have increased. 相似文献
6.
S. H. Sajjad Babar Hussain M. Ahmed Khan Asif Raza B. Zaman Ijaz Ahmed 《Climatic change》2009,96(4):539-547
Karachi is the largest city of Pakistan. The temperature change in Karachi is studied in this research by analyzing the time
series data of mean maximum temperature (MMxT), mean minimum temperature (MMiT) and mean annual temperature (MAT) from 1947
to 2005 (59 years). Data is analyzed in three parts by running linear regression and by taking anomalies of all time periods:
(a) whole period from 1947–2005; (b) phase one 1947–1975 and (c) phase two 1976–2005. During 1947 to 2005 MMxT has increased
about 4.6°C, MMiT has no change and MAT has increased 2.25°C. During 1947–1975, MMxT increased 1.9°C, in this period there
is − 1.3°C decrease in MMiT and MAT has raised upto 0.3°C. During 1976–2005, the MMxT, MMiT and MAT increased 2.7°C, 1.2°C
and 1.95°C, respectively. The analysis shows significantly the role of extreme vulnerability of MMxT in rising the temperature
of Karachi than the MMiT. 相似文献
7.
Annual methane emission from Finnish mires estimated from eddy covariance campaign measurements 总被引:4,自引:0,他引:4
K. J. Hargreaves D. Fowler C. E. R. Pitcairn M. Aurela 《Theoretical and Applied Climatology》2001,70(1-4):203-213
Summary Measurements of landscape-scale methane emission were made over an aapa mire near Kaamanen in Finnish Lapland (69° 8′ N,
27° 16′ E, 155 m ASL). Emissions were measured during the spring thaw, in summer and in autumn. No effect of water table position
on CH4 emission was found as the water table remained at or above the surface of the peat. Methane emission fluxes increased with
surface temperature from which an activation energy of −99 kJ mol−1 was obtained. Annual emission from the site, modelled from temperature regression and short-term flux measurements made in
three separate years, was calculated to be 5.5 ± 0.4 g CH4 m−2 y−1 of which 0.6 ± 0.1 g CH4 m−2 y−1 (11%) was released during the spring thaw which lasted 20 to 30 days.
The effect of global warming on the CH4 budget of the site was estimated using the central scenario of the SILMU (Finnish Research Programme on Climate Change) model
which predicts annual mean temperature increases of 1.2, 2.4 and 4.4 °C in 2020, 2050 and 2100, respectively. Maximum enhancements
in CH4 emission due to warming were calculated to be 18, 40 and 84% for 2020, 2050 and 2100, respectively. Actual increases may
be smaller because prediction of changes in water table are highly uncertain.
Received September 17, 1999 Revised October 16, 2000 相似文献
8.
Summary Spatial-temporal characteristics of temperature variations were analyzed from China daily temperature based on 486 stations
during the period 1960–2000. The method of hierarchical cluster analysis was used to divide the territory into sub-regional
areas with a coherent evolution, both annually and seasonally. Areas numbering 7–9 are chosen to describe the regional features
of air temperature in mainland China.
All regions in mainland China experienced increasing trends of annual mean temperature. The trend of increasing temperature
was about 0.2–0.3 °C/10 yr in northern China and less than 0.1 °C/10 yr in southern China. In the winter season, the increasing
trend of temperature was about 0.5–0.7 °C/10 yr in northern China and about 0.2–0.3 °C/10 yr in southern China. The increasing
trend of autumn temperature was mainly located in northwestern China and southwestern China including the Tibetan Plateau.
In spring, the rising trend of temperature was concentrated in Northeast China and North China while there was a declining
temperature trend of −0.13 °C/10 yr in the upper Yangtze River. In summer, the declining trend of temperature was only concentrated
in the mid-low valley of the Yangtze and Yellow Rivers while surrounding this valley there were increasing trends in South
China, Southwest China, Northwest China, and Northeast China.
Rapid changes in temperature in various regions were detected by the multiple timescale t-test method. The year 1969 was a rapid change point from a high temperature to a low temperature along the Yangtze River
and South China. In the years 1977–1979, temperature significantly increased from a lower level to a higher level in many
places except for regions in North China and the Yangtze River. Another rapid increasing temperature trend was observed in
1987. In the years 1976–1979, a positive rapid change of summer temperature occurred in northwestern China and southwestern
China while a decreasing temperature was found between the Yellow River and the Yangtze River. A rapid increase of winter
temperature was found for 1977–1979 and 1985–1986 in many places.
There were increasing events of extreme temperature in broad areas except in the north part of Northeast China and the north
part of the Xinjiang region. In winter, increasing temperature of the climate state and weakening temperature extremes are
observed in northern China. In summer, both increasing temperature of the climate state and enhancing temperature extremes
were commonly exhibited in northern China.
Present address: Linfen Meteorological Office, Linfen 041000, Shanxi Province, China. 相似文献
9.
An analysis of simulated future surface climate change over the southern half of Korean Peninsula using a RegCM3-based high-resolution
one-way double-nested system is presented. Changes in mean climate as well as the frequency and intensity of extreme climate
events are discussed for the 30-year-period of 2021–2050 with respect to the reference period of 1971–2000 based on the IPCC
SRES B2 emission scenario. Warming in the range of 1–4°C is found throughout the analysis region and in all seasons. The warming
is maximum in the higher latitudes of the South Korean Peninsula and in the cold season. A large reduction in snow depth is
projected in response to the increase of winter minimum temperature induced by the greenhouse warming. The change in precipitation
shows a distinct seasonal variation and a substantial regional variability. In particular, we find a large increase of wintertime
precipitation over Korea, especially in the upslope side of major mountain systems. Summer precipitation increases over the
northern part of South Korea and decreases over the southern regions, indicating regional diversity. The precipitation change
also shows marked intraseasonal variations throughout the monsoon season. The temperature change shows a positive trend throughout
2021–2050 while the precipitation change is characterized by pronounced interdecadal variations. The PDF of the daily temperature
is shifted towards higher values and is somewhat narrower in the scenario run than the reference one. The number of frost
days decreases markedly and the number of hot days increases. The regional distribution of heavy precipitation (over 80 mm/day)
changes considerably, indicating changes in flood vulnerable regions. The climate change signal shows pronounced fine scale
signal over Korea, indicating the need of high-resolution climate simulations 相似文献
10.
Summary We have examined station data from around the world to study the separate effects of the latitude (between 60° N–40° S),
elevation and distance inland, on the annual-mean screen temperature. In the first 200–400 km from some west coasts, screen
temperatures (after adjustment for elevation) rise inland, reaching a maximum called the ‘thermal-ridge temperature’ Tr. The
rise of temperature within this littoral fringe (of width F) depends mainly on the difference between the sea-surface temperature
off the west coast and the zonal mean. Further inland than such a fringe, adjusted temperatures generally decline eastwards,
approximately linearly, at a rate C. The rate is related to hemisphere and latitude.
Empirical relationships between latitude and the observed coastal sea-surface temperature, the near-shore screen temperature,
Tr, C and F for each continent are used to estimate annual mean temperatures on land. Independent estimates of this kind for
48 places, using a look-up table, differ overall by only 0.7 K from the actual long-term average annual mean temperatures.
This is less than half the error resulting from an assumption of zonal-mean temperatures. Basing estimates on coastal sea-surface
temperatures, instead of the look-up table, results in an average error of 1.0 K for the 48 places. The errors are comparable
with the standard deviation of annual mean temperatures during 30 years or so.
Received March 6, 2001 Revised July 30, 2001 相似文献
11.
Summary The Siberian High is the most important atmospheric centre of action in Eurasia during the winter months. Here its variability
and relationship with temperature and precipitation is investigated for the period 1922 to 2000. The pronounced weakening
of the Siberian High during the last ∼ 20 years is its most remarkable feature. Mean temperature, averaged over middle to
high latitude Asia (30° E–140° E, 30° N–70° N), is correlated with the Siberian High central intensity (SHCI) with correlation
coefficient of − 0.58 (1922–1999), and for precipitation, the correlation coefficient is − 0.44 (1922–1998). Taking the Arctic
Oscillation (AO), the SHCI, the Eurasian teleconnection pattern (EU), and the Southern Oscillation (SO) index into account,
72 percent of the variance in temperature can be explained for the period 1949–1997 (for precipitation the variance is 26
percent), with the AO alone explaining 30 percent of the variance, and the Siberian High contributing 24 percent. The precipitation
variance explained by the Siberian High is only 9.8 percent of the total.
Received January 2, 2001 Revised November 24, 2001 相似文献
12.
Annual precipitation, July and January temperatures were reconstructed from a continuous Holocene pollen sequence from the
Middle Atlas, Morocco, using the best modern analogues method. The reconstructions show a clear difference between the early
and late Holocene: from ∼10 ka to ∼6.5 ka the climate was drier and warmer than during the period since 6.5 ka. The average
value of annual precipitation was ∼870 mm until 6.5 ka, then rose to ∼940 mm. Between 10 ka and 6.5 ka January and July temperatures
were about 4 °C higher than the present. Both temperatures show a marked decrease between 7 ka and 6 ka. After 6.5 ka July
and January temperatures fluctuated between 21 and 23 °C, and 2.5 and 5 °C respectively. January temperatures show a period
of intermediate values (∼3.5 °C) between 4 ka and 5.5 ka. The reconstructed climate values generally match palaeolimnological
data from the same core, which show five intervals of low lake level during the Holocene. They are also consistent with regional-scale
COHMAP simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of
Africa and the intertropical band.
Received: 7 July 1997 / Accepted: 28 May 1998 相似文献
13.
The Urban Heat Island Effect at Fairbanks, Alaska 总被引:13,自引:0,他引:13
Summary Using climatic data from Fairbanks and rurally situated Eielson Air Force Base in Interior Alaska, the growth of the Fairbanks
heat island was studied for the time period 1949 – 1997. The climate records were examined to distinguish between a general
warming trend and the changes due to an increasing heat island effect. Over the 49-year period, the population of Fairbanks
grew by more than 500%, while the population of Eielson remained relatively constant. The mean annual heat island observed
at the Fairbanks International Airport grew by 0.4 °C, with the winter months experiencing a more significant increase of
1.0 °C. Primary focus was directed toward long-term heat island characterization based on season, wind speed, cloud cover,
and time of day. In all cases, the minima temperatures were affected more than maxima and periods of calm or low wind speeds,
clear winter sky conditions, and nighttime exhibited the largest heat island effects.
Received August 17, 1998 Revised March 26, 1999 相似文献
14.
Michelle T. H. van Vliet Stephen Blenkinsop Aidan Burton Colin Harpham Hans Peter Broers Hayley J. Fowler 《Climatic change》2012,111(2):249-277
Regional or local scale hydrological impact studies require high resolution climate change scenarios which should incorporate
some assessment of uncertainties in future climate projections. This paper describes a method used to produce a multi-model
ensemble of multivariate weather simulations including spatial–temporal rainfall scenarios and single-site temperature and
potential evapotranspiration scenarios for hydrological impact assessment in the Dommel catchment (1,350 km2) in The Netherlands and Belgium. A multi-site stochastic rainfall model combined with a rainfall conditioned weather generator
have been used for the first time with the change factor approach to downscale projections of change derived from eight Regional
Climate Model (RCM) experiments for the SRES A2 emission scenario for the period 2071–2100. For winter, all downscaled scenarios
show an increase in mean daily precipitation (catchment average change of +9% to +40%) and typically an increase in the proportion
of wet days, while for summer a decrease in mean daily precipitation (−16% to −57%) and proportion of wet days is projected.
The range of projected mean temperature is 7.7°C to 9.1°C for winter and 19.9°C to 23.3°C for summer, relative to means for
the control period (1961–1990) of 3.8°C and 16.8°C, respectively. Mean annual potential evapotranspiration is projected to
increase by between +17% and +36%. The magnitude and seasonal distribution of changes in the downscaled climate change projections
are strongly influenced by the General Circulation Model (GCM) providing boundary conditions for the RCM experiments. Therefore,
a multi-model ensemble of climate change scenarios based on different RCMs and GCMs provides more robust estimates of precipitation,
temperature and evapotranspiration for hydrological impact assessments, at both regional and local scale. 相似文献
15.
Summary Degree-days as a measure of accumulated temperature deviations from a base temperature have many practical applications in
various human related activities such as home cooling, heating, plant growth in agriculture and power generation in addition
to energy requirement. Long temperature records are necessary for their reliable estimations at given stations. In this paper,
degree-day measure has been applied to monthly temperature records for systematically changed base temperature values from
− 25 °C to + 35 °C with 5 °C increments at 255 meteorology stations in Turkey. The results are represented in the form of
spatial degree-day distribution maps, which are then related to various climatic, meteorological and topographic features
of Turkey. For instance, free surface water bodies in forms of surrounding seas, lakes and rivers insert retardation in the
expansion of heating degree-days over large regions. On the other hand, cold air penetration from polar regions in the northeastern
Turkey originating from Siberia appears at moderate base temperature heating degree-days.
Received August 20, 1998 Revised June 21, 1999 相似文献
16.
Tropical climates at the Last Glacial Maximum: a new synthesis of terrestrial palaeoclimate data. I. Vegetation, lake-levels and geochemistry 总被引:1,自引:1,他引:0
I. Farrera S. P. Harrison I. C. Prentice G. Ramstein J. Guiot P. J. Bartlein R. Bonnefille M. Bush W. Cramer U. von Grafenstein K. Holmgren H. Hooghiemstra G. Hope D. Jolly S.-E. Lauritzen Y. Ono S. Pinot M. Stute G. Yu 《Climate Dynamics》1999,15(11):823-856
Palaeodata in synthesis form are needed as benchmarks for the Palaeoclimate Modelling Intercomparison Project (PMIP). Advances
since the last synthesis of terrestrial palaeodata from the last glacial maximum (LGM) call for a new evaluation, especially
of data from the tropics. Here pollen, plant-macrofossil, lake-level, noble gas (from groundwater) and δ18O (from speleothems) data are compiled for 18±2 ka (14C), 32 °N–33 °S. The reliability of the data was evaluated using explicit criteria and some types of data were re-analysed
using consistent methods in order to derive a set of mutually consistent palaeoclimate estimates of mean temperature of the
coldest month (MTCO), mean annual temperature (MAT), plant available moisture (PAM) and runoff (P-E). Cold-month temperature
(MAT) anomalies from plant data range from −1 to −2 K near sea level in Indonesia and the S Pacific, through −6 to −8 K at
many high-elevation sites to −8 to −15 K in S China and the SE USA. MAT anomalies from groundwater or speleothems seem more
uniform (−4 to −6 K), but the data are as yet sparse; a clear divergence between MAT and cold-month estimates from the same
region is seen only in the SE USA, where cold-air advection is expected to have enhanced cooling in winter. Regression of
all cold-month anomalies against site elevation yielded an estimated average cooling of −2.5 to −3 K at modern sea level,
increasing to ≈−6 K by 3000 m. However, Neotropical sites showed larger than the average sea-level cooling (−5 to −6 K) and
a non-significant elevation effect, whereas W and S Pacific sites showed much less sea-level cooling (−1 K) and a stronger
elevation effect. These findings support the inference that tropical sea-surface temperatures (SSTs) were lower than the CLIMAP
estimates, but they limit the plausible average tropical sea-surface cooling, and they support the existence of CLIMAP-like
geographic patterns in SST anomalies. Trends of PAM and lake levels indicate wet LGM conditions in the W USA, and at the highest
elevations, with generally dry conditions elsewhere. These results suggest a colder-than-present ocean surface producing a
weaker hydrological cycle, more arid continents, and arguably steeper-than-present terrestrial lapse rates. Such linkages
are supported by recent observations on freezing-level height and tropical SSTs; moreover, simulations of “greenhouse” and
LGM climates point to several possible feedback processes by which low-level temperature anomalies might be amplified aloft.
Received: 7 September 1998 / Accepted: 18 March 1999 相似文献
17.
Summary By analyzing 12-year (1979–1990) 200 hPa wind data from National Centers for Environmental Prediction-National Center for
Atmospheric Research reanalysis, we demonstrate that the intraseasonal time scale (30–60 days) variability of the Tropical
Easterly Jet (TEJ) reported in individual case studies occurs during most years. In the entrance region (east of ∼70° E),
axis of the TEJ at 200 hPa is found along the near equatorial latitudes during monsoon onset/monsoon revivals and propagates
northward as the monsoon advances over India. This axis is found along ∼5° N and ∼15° N during active monsoon and break monsoon
conditions respectively. Examination of the European Centre for Medium Range Weather Forecasts reanalysis wind data also confirms
the northward propagation of the TEJ on intraseasonal time scales.
During the intraseasonal northward propagations, axis of the TEJ is found about 10°–15° latitudes south of the well-known
intraseasonally northward propagating monsoon convective belts. Because of this 10°–15° displacement, axis of the TEJ arrives
over a location about two weeks after the arrival of the monsoon convection. Systematic shifting of the locations by convection,
low level monsoon flow and TEJ in a collective way during different phases of the monsoon suggests that they all may be related. 相似文献
18.
Summary A mesoscale convective system (MCS) case that developed over the Yellow Sea (12–13 July 1993) is studied by using a 23-level,
30 km-mesh Penn State/NCAR mesoscale model MM5. This MCS was generated in northern China, south of the Changma front, in a
convectively unstable environment, under the influence of a short-wave trough accompanied by a marked cold vortex aloft.
The model with all model physics (refereed to as CNTL) captured the major features of this MCS. A mesoscale low-level jet
(mLLJ), with a horizontal scale of a few hundred km, developed within the MCS. Available wind data support the realism of
this mLLJ. This mLLJ not only transports convectively unstable air directly toward the MCS but is also responsible for a strong
low-level convergence in the MCS. At 200 hPa, an anticyclonic northwesterly flow with a relatively high wind speed core on
the east of MCS was simulated. This relatively high-speed flow can be regarded as a mesoscale upper level jet (mULJ), acted
as an upper outflow over the MCS. Low-level convergence on the left-front of the mLLJ and upper divergence in the right-rear
of the mULJ creates a strong upward motion (≅ 40 cm s−1) in the MCS.
Heavy precipitation up to 45 mm between 1800–2100 UTC was observed after this MCS landed on the southern Korean Peninsula.
The CNTL run captured this heavy rainfall event. A maximum rainfall of 50 mm 3 h−1 was simulated. In another experiment, with surface sensible and moisture fluxes withheld (NOSF), the 3-h simulated rainfall
was decreased to 30 mm. Less latent heat released in the NOSF led to a weaker MCS and mLLJ. The concurrent surface fluxes
sustained a high low-level moisture field over the Yellow Sea, which helped the development of the MCS and enhanced its precipitation
in this case.
Received January 8, 1999 相似文献
19.
Seasonal carbon dioxide balance and respiration of a high-arctic fen ecosystem in NE-Greenland 总被引:2,自引:0,他引:2
C. Nordstroem H. Soegaard T. R. Christensen T. Friborg B. U. Hansen 《Theoretical and Applied Climatology》2001,70(1-4):149-166
Summary Turbulent fluxes of CO2 were continuously measured by eddy correlation for three months in 1997 over a gramineous fen in a high-arctic environment
at Zackenberg (74°28′12″N, 20°34′23″W) in NE-Greenland. The measurements started on 1 June, when there was still a 1–2 m cover
of dry snow, and ended 26 August at a time that corresponds to late autumn at this high-arctic site. During the 20-day period
with snow cover, fluxes of CO2 to the atmosphere were small, typically 0.005 mg CO2 m−2 s−1 (0.41 g CO2 m−2 d−1), wheres during the thawed period, the fluxes displayed a clear diurnal variation. During the snow-free period, before the
onset of vegetation growth, fluxes of CO2 to the atmosphere were typically 0.1 mg CO2 m−2 s−1 in the afternoon, and daily sums reached values up to almost 9 g CO2 m−2 d−1. After 4 July, downward fluxes of CO2 increased, and on sunny days in the middle of the growing season, the net ecosystem exchange rates attained typical values
of about −0.23 mg m−2 s−1 at midday and max values of daily sums of −12 g CO2 m−2 d−1. Throughout the measured period the fen ecosystem acted as a net-sink of 130 g CO2 m−2. Modelling the ecosystem respiration during the season corresponded well with eddy correlation and chamber measurements.
On the basis of the eddy correlation data and the predicted respiration effluxes, an estimate of the annual CO2 balance the calender year 1997 was calculated to be a net-sink of 20 g CO2 m−2 yr−1.
Received October 6, 1999 Revised May 2, 2000 相似文献
20.
M. R. Van den Broeke 《Climate Dynamics》2000,16(5):369-377
We use NCEP/NCAR reanalysis data to study the impact of the semiannual oscillation (SAO) on the annual cycle of Antarctic
near-surface temperature. When the SAO is weak, the contracted phases (March/April and September/October) are warm and the
expanded phases (December/January and June/July) cold. This pattern is explained in terms of the changing meridional fetch
of the circumpolar pressure trough. Because of the wave number three character of the SAO, large regional deviations are found.
For instance, enhanced north-westerly flow in the second expansion phase (June/July) of weak SAO years limits the growth of
the sea ice in the Amundsen and Bellingshausen seas, leading to anomalously high temperatures in the Antarctic Peninsula region.
The short (<50 year) temperature records at Antarctic stations still carry the fingerprint of decadal SAO variability. By
matching the observed monthly temperature trends to the patterns derived from the gridded re-analysis, we propose a background
Antarctic warming trend for the second expansion phase (June/July) of 4.62 ± 1.02 °C per century, four times the annual value.
Received: 23 August 1999 / Accepted: 28 October 1999 相似文献