Seasonal variations of the near surfacelayer parameters over the Antarctic ice sheet in Princess Elizabeth Land,East Antarctica

Analysis of sensible heat flux(Qh),latent heat flux(Qe),Richardson number(Ri),bulk transport coefficient(Cd) and katabatic winds are presented by using the meteorological data in the near surface layer from an automatic weather station(AWS) in Princess Elizabeth Land,East Antarctica ice sheet and the data of corresponding period at Zhongshan station in 2002.It shows that annual mean air temperature at LGB69 is-25.6°C,which is 16.4°C lower than that at Zhongshan,where the elevation is lower and located on the coast.The temperature lapse rate is about 1.0°C/110 m for the initial from coast to inland.The turbulence heat flux at LGB69 displays obvious seasonal variations with the average sensible heat flux-17.9 W/m2 and latent heat flux-0.9 W/m2.The intensity(Qh Qe) of coolling source is-18.8 W/m2 meaning the snow surface layer obtains heat from atmosphere.The near surface atmosphere is near-neutral stratified with bulk transport coefficients(Cd) around 2.8×10-3,and it is near constant when the wind speed higher than 8 m/s.The speed and the frequency of easterly Katabatic winds at LGB69 were higher than that at Zhongshan Station.     

Analyses of structure of planetary boundary layer in ice camp over Arctic ocean

The vertical structure of Planetary boundary layer over Arctic floating ice is presented by using about 50 atmospheric profiles and relevant data sounded at an ice station over Arctic Ocean from 22 August to 3 September,2003.It shows that the height of the convective boundary layer in day is greater than that of the stability boundary layer in night.The boundary layer can be described as vertical structures of stability,instability and multipling The interaction between relative warm and wet down draft air from up level and cool air of surface layer is significant,which causes stronger wind shear,temperature and humidity inversion with typical wind shear of 10 m/s/100 m,intensity of temperature inversion of 8 ℃/100 m.While the larger pack ice is broken by such process,new ice free area in the high latitudes of arctic ocean.The interactions between air/ice/water are enhanced.The fact helps to understanding characteristics of atmospheric boundary layer and its effect in Arctic floating ice region.     

复杂山区地形条件下ERA5再分析地表气温降尺度方法

高时空分辨率的气温栅格数据是多种地学模型和气候模型的重要输入。山区地形复杂,气温空间异质性强,如何获取高时空分辨率的山区地表气温数据一直是研究热点与难点。本文选择地形复杂的河北省张家口市作为试验区,基于局部薄盘样条函数对ERA5再分析日均近地表气温（2 m高度）进行空间插值,并利用随机森林算法,结合少量气象站观测气温数据、地形地表参数数据构建日均气温订正模型和气温逐时化模型,实现空间分辨率由0.1 °（约11 km）到30 m的逐时气温降尺度,最后将该模型拓展应用于其他时间与区域,检验本文发展的降尺度方法在没有站点观测数据条件下的时空移植性。结果显示,本文降尺度方法得到的高时空分辨率山区气温数据精度较高,1月均方根误差（RMSE）平均值为2.4 ℃,明显优于气象站点插值结果,且气温相对高低的空间分布更为合理、纹理更加丰富;将该方法应用到其他时间与区域的RMSE平均值分别为2.9 ℃与2.5 ℃,均小于再分析资料直接插值所产生的误差。研究结果总体表明,在气象站点较少甚至没有时,可利用本文方法通过ERA5再分析气温准确获取复杂地形条件下的山区高时空分辨率气温数据。     

基于局地气候分区的济南市热环境空间分异及其 影响因素

城市地表覆被及空间结构不同,导致热岛效应不同,城市热环境存在空间差异。局地气候分区（LCZ）在城市热岛研究方面得到了广泛应用。合理划分LCZ、科学制定LCZ分类标准,是基于LCZ研究城市热岛的关键技术问题。本文基于济南市城市路网、DEM和建筑大数据划分LCZ,利用Landsat 8遥感影像反演地表温度,采用克里金法进行气温空间插值,以地表温度和气温综合表达城市热环境。在此基础上,采用方差分析方法研究了城市热环境的空间分异特征和LCZ类内热环境差异,采用相关分析方法研究了城市热环境的影响因素。结果表明：① 济南市地表温度和4:00、8:00、14:00的气温空间分布格局差异明显,存在较高温度异常值的LCZ数量分别占全市LCZ总数的0.25%、1.60%、4.05%和3.96%。建筑密集区域地表温度较高,同时包含分散的较高气温区,呈现热岛效应;② 不同类型LCZ的地表温度和不同时刻气温平均值存在明显差异。高层低密度、高层中密度、中层低密度等类型存在较高气温异常值的数量分别占较高异常值总数的47.37%和33.33%、9.65%,类内热岛效应明显;③ LCZ类型不同,类内热岛效应存在差异。低层低密度、中层低密度、高层低密度和高层中密度等类型所处位置高程不同,其方差分析的P值均小于0.05,热岛效应存在显著差异;④ LCZ所处位置高程不同,建筑空间分布指标对城市热环境的影响各异。总体而言,地表温度与建筑平均高度呈负相关,且达到了0.05以上的显著性水平,而气温与之呈正相关,且达到了0.001的显著性水平;城市热环境与建筑基底面积及建筑体积的平均值和标准差、建筑密度、容积率等指标的正相关性达到了0.001的显著性水平,这些指标对城市热环境的正向影响作用明显。     

A temperature inversion in "Chinese Arctic Research Expedition 1999

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Elevated Ducts and Low Clouds over the Central Western Pacific Ocean in Winter Based on GPS Soundings and Satellite Observation

Both low clouds and elevated ducts are common phenomena in the oceanic atmosphere. Low clouds affect elevated ducts by changing the structure of atmospheric temperature and humidity. However, due to the limitation of met-ocean measurements, research on them is still scattered. This paper presents the distribution of elevated ducts and clouds over the central Western Pacific Ocean(WPO) based on Global Position System(GPS) sounding data and Himawari-8 satellite products from November 2015 to January 2016. Results show that the frequency of elevated ducts detected by ship-based GPS soundings was as high as 77% over the central WPO. The height and frequency of elevated ducts are closely related to the low clouds. If there are no clouds, the occurrence probability and mean base height of the elevated ducts are 14% and 730 m, respectively. By comparison, the occurrence probability and mean base height increase up to 24% and 1471 m, respectively, in the presence of cumulus(Cu) clouds, and 22% and 1511 m, respectively, in the presence of stratocumulus(Sc) clouds. Elevated ducts occur near the cloud top. The analysis of geopotential height and wind fields from the European Centre for Medium-Range Weather Forecasts(ECMWF) reanalysis dataset(ERA-interim) shows that the study area is covered by a strong and stable subtropical high, and slowly sinking dry air masses inside the subtropical high are above the moist boundary-layer air mass. The appearance and evolution of low clouds will adjust the temperature and humidity structure of the lower troposphere. If there are no clouds, the marine boundary layer(MBL) is the classic mixed boundary layer. Humidity gradient and subsidence inversion are formed atop the mixed layer. When low clouds are present, long wave radiation and entrainment atop clouds form a strong temperature inversion and humidity gradient, which strengthen elevated ducts. However, when Sc clouds are decoupled, a weaker temperature inversion and humidity gradient may occur between the surface mixed layer and subcloud layer, leading to a weak elevated duct atop the mixed layer.     

Northern-Hemisphere snow cover patterns and formation conditions in winter 2007 and 2012

The Arctic sea ice minimum records appeared in the Septembers of 2007 and 2012, followed by high snow cover areas in the Northern Hemisphere winters. The snow cover distributions show different spatial patterns in these two years: increased snow cover in Central Asia and Central North America in 2007, while increased snow cover in East Asia and northwestern Europe in 2012. The high snow cover anomaly shifted to higher latitudes in winter of 2012 compared to 2007. It is noticed that the snow cover had positive anomaly in 2007 and 2012 with the following conditions: the negative geopotential height and the related cyclonic wind anomaly were favorable for upwelling, and, with the above conditions, the low troposphere and surface air temperature anomaly and water vapor anomaly were favorable for the formation and maintenance of snowfalls. The negative geopotential height, cyclonic wind and low air temperature conditions were satisfied in different locations in 2007 and 2012, resulting in different spatial snow cover patterns. The cross section of lower air temperature move to higher latitudes in winter of 2012 compared to 2007.     

Numerical simulation of the impact of underlying surface changes on Arctic climate

Using a regional atmospheric model for Arctic climate simulation, two groups of numerical experiments were carried out to study the inlfuence of changes in the underlying surface (land surface, sea sur...     

An Assessment of Snow Cover Duration Variability Among Three Basins of Songhua River in Northeast China Using Binary Decision Tree

The dynamics of snow cover differs greatly from basin to basin in the Songhua River of Northeast China, which is attributable to the differences in the topographic shift as well as changes in the vegetation and climate since the hydrological year (HY) 2003. Daily and flexible multi-day combinations from the HY 2003 to 2014 were produced using Moderate Resolution Imaging Spectroradiometer (MODIS) from Terra and Aqua remote sensing satellites for the snow cover products in the three basins including the Nenjiang River Basin (NJ), Downstream Songhua River Basin (SD) and Upstream Songhua River Basin (SU). Snow cover duration (SCD) was derived from flexible multiday combination each year. The results showed that SCD was significantly associated with elevation, and higher SCD values were found out in the mountainous areas. Further, the average SCDs of NJ, SU and SD basins were 69.43, 98.14 and 88.84 d with an annual growth of 1.36, 2.04 and 2.71 d, respectively. Binary decision tree was used to analyze the nonlinear relationships between SCD and six impact factors, which were successfully applied to simulate the spatial distribution of depth and water equivalent of snow. The impact factors included three topographic factors (elevation, aspect and slope), two climatic factors (precipitation and air temperature) and one vegetation index (Normalized Difference Vegetation Index, NDVI). By treating yearly SCD values as dependent variables and six climatic factors as independent variables, six binary decision trees were built through the combination classification and regression tree (CART) with and without the consideration of climate effect. The results from the model show that elevation, precipitation and air temperature are the three most influential factors, among which air temperature is the most important and ranks first in two of the three studied basins. It is suggested that SCD in the mountainous areas might be more sensitive to climate warming, since precipitation and air temperature are the major factors controlling the persistence of snow cover in the mountainous areas.     

Seasonal Variation in Air Temperature and Relative Humidity on Building Areas and in Green Spaces in Beijing,China

The cooling and humidifying effects of urban parks are an essential component of city ecosystems in terms of regulating microclimates or mitigating urban heat islands(UHIs).Air temperature and relative humidity are two main factors of thermal environmental comfort and have a critical impact on the urban environmental quality of human settlements.We measured the 2-m height air temperature and relative humidity at the Beijing Olympic Park and a nearby building roof for more than 1 year to elucidate seasonal variations in air temperature and relative humidity,as well as to investigate the outdoor thermal comfort.The results showed that the lawn of the park could,on average,reduce the air temperature by(0.80±0.19)℃,and increase the relative humidity by(5.24±2.91)% relative to the values measured at the building roof during daytime.During the nighttime,the lawn of the park reduced the air temperature by(2.64±0.64)℃ and increased the relative humidity by(10.77±5.20)%.The park was cooler and more humid than surrounding building area,especially in night period(more pronounced cooling with 1.84℃).Additionally,the lawn of the park could improve outdoor thermal comfort through its cooling and humidifying effects.The level of thermal comfort in the park was higher than that around the building roof for a total of 11 days annually in which it was above one or more thermal comfort levels(average reduced human comfort index of 0.92)except during the winter.     

Energy Budget over Seasonal Snow Surface at an Open Site and Beneath Forest Canopy Openness during the Snowmelt Period in Western Tianshan Mountains,China

In this study, meteorological factors and snowmelt rate at an open site on sunny slope(OPS) and beneath forest canopy openness on shady slope(BFC) were measured using an automatic weather station and snow lysimeter during the snowmelt period in 2009, 2010 and 2013. The energy budget over snow surface was calculated according to these meteorological datasets. The analysis results indicated that the net shortwave radiation(K) and sensible heat flux(H) were energy sources, and the latent heat flux(LVE) was energy sinks of snow surfaces at all sites. The net longwave radiation(L) was energy sink at OPS and 80% BFC, but energy source at 20% BFC. The gain of K, H, and the loss of LVE at BFC were obviously lower than those at OPS. The L was the maximum difference of energy budget between snow surface at BFC and OPS. In warm and wet years, the most important factor of the energy budget variation at OPS was air humidity and the second mostimportant factor was air temperature. However, the ground surface temperature on the sunny slope was the most important factor for L and energy budget at BFC. With the increases in forest canopy openness and the slope of adjacent terrains, the influences of ground surface temperature on the sunny slope on L and the energy budget over snow surface at BFC increased, especially when the snow cover on the sunny slope melts completely.     

顾及多因子影响的中国西部地区大气加权平均温度模型精化研究

针对中国西部地区地形起伏较大等情况,分析大气加权平均温度（T_m）与测站高程、地面温度的关系,利用2014～2016年探空数据,在Bevis模型基础上建立一种与地面温度、高程和季节变化有关的新T_m模型。以2017年探空数据为参考值,对新模型进行精度分析,并与广泛使用的Bevis模型和GPT2w模型进行精度比较。结果表明,以探空数据为参考值,新模型的年均偏差和均方根误差（RMS）分别为-0.08 K和3.89 K,相比Bevis模型、GPT2w-5模型和GPT2w-1模型,其精度（RMS值）分别提高14.3%、20.6%和9.3%。此外,将新T_m模型用于GNSS水汽计算,其水汽计算理论RMS误差和相对误差分别为0.22 mm和1.43%,新模型在中国西部地区的GNSS水汽探测中具有重要的应用价值。     

Local variability in temperature, humidity and radiation in the BaekduDaegan Mountain protected area of Korea

A novel embedded sensor network records changes in key climatic-environmental variables over a range of altitude in the BaekduDaegan Mountain (BDM) of Gangwon Province in Korea, a protected mountain region with unique biodiversity undergoing climate change research. The investigated area is subdivided into three horizontal north-south study areas. Three variables, temperature (T, ℃), relative humidity (RH, %), and light intensity (LI, lumens m -2 , or lux, lx), have been continuously measured at hourly intervals from June, 2010 to September, 2011 using HOBO H8 devices at 10 fixed study sites. These hourly observations are aggregated to monthly, seasonal and annual mean values, and results are summarized to inaugurate a long-term climate change investigation. A region wide T difference in accordance with altitude, or lapse rate, over the interval is calculated as 0.4℃100 m -1 . T lapse rates change seasonally, with winter lapse rates being greater than those of summer. RH is elevated in summer compared to other seasons. LI within forestland is lower during summer and higher during other seasons. The obtained results could closely relate to the vegetation type and structure and the terrain state since data loggers were located in forestland.     

基于GIS的“一带一路”地区气温插值方法比较研究

“一带一路”倡议是新时期中国为加强对外开放提出的全球化合作倡议,资源环境的优化配置对全球化发展意义重大。气温作为重要的基础数据和输入要素,对其进行空间化处理是实现大尺度区域资源环境优化配置的前提。本文基于地理信息技术（GIS）,运用距离平方反比法（IDS）、协同克里格法（CK）、回归距离平方反比法（RIDS）和回归协同克里格法（RCK）,对“一带一路”地区1980—2017年的2679个气象站点的月平均气温和年平均气温数据进行插值,获得了“一带一路”地区10 km分辨率的气温空间分布数据。交叉验证结果表明：① IDS、CK、RIDS和RCK插值法在整体上均较好地展示了“一带一路”地区气温的地理空间分布规律,4种插值方法的月均气温的均方根误差分别在1.93~2.43、1.78~2.14、1.31~2.23和1.23~1.92 ℃之间;年均气温的均方根误差分别为1.94、1.83、1.37和1.27 ℃;② 在“一带一路”地区,加入协变量分析的CK插值精度整体优于IDS,并且削弱了IDS的极值现象;③ RIDS和RCK对年均气温的插值精度分别较IDS和CK提高了29.4%和30.6%,表明加入地理要素并进行残差修正的插值精度得到了进一步提高。总体来看,RCK插值法对气温数据的插值精度最高,可以考虑将此方法作为“一带一路”地区温度等气象要素的插值方法。     

The first geodetic investigation at the summit of Dome A,Antarctica

Dome A is the highest ice feature in the Antarctica,up to now,little is known about surface topography at Dome A.The first Chinese ITASE expedition was carried out from Zhongshan station to Dome A during the 1996/1997 austral summer. During the 2004/2005 austral summer,the traverse was extended to the summit of Dome A which is 1228 km from Zhongshan Station by 21st Chinese National Antarctic Research Expedition (CHINARE).The real-time kinematic (RTK) GPS survey was carried out in the summit of Dome A dur...     

Response of snow hydrological processes to a changing climate during 1961 to 2016 in the headwater of Irtysh River Basin,Chinese Altai Mountains

With changing climatic conditions and snow cover regime, regional hydrological cycle for a snowy basin will change and further available surface water resources will be redistributed. Assessing snow meltwater effect on runoff is the key to water safety, under climate warming and fast social-economic developing status. In this study, stable isotopic technology was utilized to analyze the snow meltwater effect on regional hydrological processes, and to declare the response of snow hydrology to climate change and snow cover regime, together with longterm meteorological and hydrological observations, in the headwater of Irtysh River, Chinese Altai Mountains during 1961-2015. The average δ~(18) O values of rainfall, snowfall, meltwater, groundwater and river water for 2014–2015 hydrological year were-10.9‰,-22.3‰,-21.7‰,-15.7‰ and-16.0‰, respectively.The results from stable isotopes, snow melting observation and remote sensing indicated that the meltwater effect on hydrological processes in Kayiertesi River Basin mainly occurred during snowmelt supplying period from April to June. The contribution of meltwater to runoff reached 58.1% during this period, but rainfall, meltwater and groundwater supplied 49.1%, 36.9% and 14.0% of water resource to annual runoff, respectively. With rising air temperature and increasing snowfall in cold season, the snow water equivalent(SWE) had an increasing trend but the snow cover duration declined by about one month including 13-day delay of the first day and 17-day advancement of the end day during 1961–2016. Increase in SWE provided more available water resource. However, variations in snow cover timing had resulted in redistribution of surface water resource, represented by an increase of discharge percentage in April and May, and a decline in Juneand July. This trend of snow hydrology will render a deficit of water resource in June and July when the water resource demand is high for agricultural irrigation and industrial manufacture.     

利用MERRA-2地表温压资料进行中国区域GNSS水汽反演的精度分析北大核心CSCD

为分析美国宇航局发布的最新MERRA-2再分析资料地表温压产品在中国区域进行GNSS水汽反演的精度,联合中国区域609个地面气象站实测温度和气压数据、48个GNSS站及并址探空站资料,评估MERRA-2温压产品及其在GNSS PWV反演中的精度。结果表明:1)MERRA-2气压和温度年均bias分别为-0.01 hPa和0.38 K,年均RMSE分别为1.08 hPa和2.66 K,MERRA-2再分析资料温压产品在中国区域具有较高的精度;2)MERRA-2再分析资料温压产品在中国大部分地区呈现负偏差,精度从高到低依次为南方地区、北方地区、西北地区和青藏高原地区;3)将MERRA-2温压产品的PWV反演结果与并址探空站实测PWV进行对比可知,MERRA-2再分析资料温压产品反演的GNSS PWV平均RMSE为2.16 mm,能较好地反映PWV的日变化。因此,MERRA-2地表温压产品在中国区域的气象研究及GNSS水汽监测中具有重要意义。     

Snow and sea ice thermodynamics in the Arctic： Model validation and sensitivity study against SHEBA data

Evolution of the Arctic sea ice and its snow cover during the SHEBA year were simulated by applying a high-resolution thermodynamic snow/ice model （HIGHTSI）. Attention was paid to the impact of albedo on snow and sea ice mass balance, effect of snow on total ice mass balance, and the model vertical resolution. The SHEBA annual simulation was made applying the best possible external forcing data set created by the Sea Ice Model Intercomparison Project. The HIGHTSI control run reasonably reproduced the observed snow and ice thickness. A number of albedo schemes were incorporated into HIGHTSI to study the feedback processes between the albedo and snow and ice thickness. The snow thickness turned out to be an essential variable in the albedo parameterization. Albedo schemes dependent on the surface temperature were liable to excessive positive feedback effects generated by errors in the modelled surface temperature. The superimposed ice formation should be taken into account for the annual Arctic sea ice mass balance.     

结合HASM和GWR方法的省级尺度近地表气温估算

卫星遥感反演得到的地表温度可用于近地表气温的估算,但现有方法的估算精度仍有进一步提升的空间。为了获取空间上连续且精度较高的近地表气温,本研究以四川省为例,首次将高精度曲面建模（HASM）用于遥感和气温实测数据的融合,并将综合了气温、地表温度、海拔、坡度、坡向的地理加权回归（GWR）拟合结果作为HASM模型的初始温度场,进而采用此种结合HASM和GWR的求解算法（HASM-GWR）,融合MOD11C3地表温度产品与190个气象台站的气温实测数据,开展省级尺度近地表气温估算,并通过比较HASM-GWR、GWR以及普通线性回归（OLS）3种方法的估算精度,评估各模型对近地表气温的估算效果。结果表明,相比于传统估算模型,采用HASM-GWR数据融合方法能有效提高近地表气温的估算精度。采用该方法的近地表气温估算残差,72%介于-1~1 ℃,90%介于-2~2 ℃;且与GWR和OLS模型相比,估算结果的均方根误差（RMSE）分别降低了25.42%和39.83%。     

The study on fishing ground of neon flying squid, Ommastrephes bartrami, and ocean environment based on remote sensing data in the Northwest Pacific Ocean

The relationships between the neon flying squid, Ommastrephes bartrami, and the relative ocean environmental factors are analyzed. The environmental factors collected are sea surface temperature (SST), chlorophyll concentration (Chl-a) and sea surface height (SSH) from NASA, as well as the yields of neon flying squid in the North Pacific Ocean. The results show that the favorable temperature for neon flying squid living is 10℃-22℃ and the favorite temperature is between 15℃-17℃. The Chl-a concentration is 0.1-0.6 mg/m3. When Chl-a concentration changes to 0.12-0.14 mg/m3, the probability of forming fishing ground becomes very high. In most fishing grounds,the SSH is higher than the mean SSH. The generalized additive model (GAM) was applied to analyze the correlations between neon flying squid and ocean environmental factors. Every year, squids migrate northward from June to August and return southward during October-November, and the characteristics of the both migrations are very different. When squids migrate to the north, most relationships between the yields and SST are positive. The relationships are negative when squids move to southward. The relationships between the yields and Chl-a concentrations are negative from June to October, and insignificant in November. There is no obvious correlation between the catches of squid and longitude, but good with latitude.