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131.
132.
Jessica R. Rodysill James M. Russell Satria Bijaksana Erik T. Brown La Ode Safiuddin Hilde Eggermont 《Journal of Paleolimnology》2012,47(1):125-139
Variations in the location and strength of convection in the Western Pacific Warm Pool (WPWP) have a profound impact on the
distribution and amount of global rainfall. Much of the variability in WPWP convection is attributed to variations in the
El Ni?o-Southern Oscillation, for which the long-term trends and forcing mechanisms remain poorly understood. Despite the
importance of WPWP convection to global climate change, we have very few paleohydrological reconstructions from the region.
Here we present a new paleolimnologic and paleohydrologic record spanning the past 1,400 years using a multi-proxy dataset
from Lake Logung, located in East Java, Indonesia that provides insights into centennial-scale trends in warm pool hydrology.
Organic matter δ13C data indicate that East Java became wetter over the last millennium until ca. 1800 Common Era (CE), consistent with evidence
for the southward migration of the Intertropical Convergence Zone (ITCZ) during this time. Superimposed on this long-term
trend are four decade- to century-scale droughts, inferred from organic matter δ13C and calcite abundance data. They are centered at 1030, 1550, 1830, and 1996 CE. The three more recent droughts correlate
with hydrologic anomalies documented in other proxy records from the WPWP region on both sides of the equator, and the two
most recent droughts correlate in time with historically documented periods of multiple, intense El Ni?o events. Thus, our
record provides strong evidence that century-scale hydrologic variability in this region relates to changes in the Walker
Circulation. Human activity within the lake catchment is apparent since 1860 CE. 相似文献
133.
Robert J. Davy Milton J. Woods Christopher J. Russell Peter A. Coppin 《Boundary-Layer Meteorology》2010,135(1):161-175
Measurements show that on numerous occasions the low-level wind is highly variable across a large portion of south-eastern Australia. Under such conditions the risk of a large rapid change in total wind power is increased. While variability tends to increase with mean wind speed, a large component of wind variability is not explained by wind speed alone. In this work, reanalysis fields from the US National Centers for Environmental Prediction (NCEP) are statistically downscaled to model wind variability at a coastal location in Victoria, Australia. In order to reduce the dimensionality of the problem, the NCEP fields are each decomposed using empirical orthogonal function (EOF) techniques. The downscaling technique is applied to two periods in the seasonal cycle, namely (i) winter to early spring, and (ii) summer. In each case, data representing 2 years are used to form a model that is then validated using independent data from another year. The EOFs that best predict wind variability are examined. To allow for non-linearity and complex interaction between variables, all empirical models are built using random forests. Quantitatively, the model compares favourably with a simple regression of wind variability against wind speed, as well as multiple linear regression models. 相似文献
134.
Evaluating regional climate model estimates against site-specific observed data in the UK 总被引:3,自引:0,他引:3
M. Rivington D. Miller K. B. Matthews G. Russell G. Bellocchi K. Buchan 《Climatic change》2008,88(2):157-185
This paper compares precipitation, maximum and minimum air temperature and solar radiation estimates from the Hadley Centre’s
HadRM3 regional climate model (RCM), (50 × 50 km grid cells), with observed data from 15 meteorological station in the UK,
for the period 1960–90. The aim was to investigate how well the HadRM3 is able to represent weather characteristics for a
historical period (hindcast) for which validation data exist. The rationale was to determine if the HadRM3 data contain systematic
errors and to investigate how suitable the data are for use in climate change impact studies at particular locations. Comparing
modelled and observed data helps assess and quantify the uncertainty introduced to climate impact studies. The results show
that the model performs very well for some locations and weather variable combinations, but poorly for others. Maximum temperature
estimations are generally good, but minimum temperature is overestimated and extreme cold events are not represented well.
For precipitation, the model produces too many small events leading to a serious under estimation of the number of dry days
(zero precipitation), whilst also over- or underestimating the mean annual total. Estimates represent well the temporal distribution
of precipitation events. The model systematically over-estimates solar radiation, but does produce good quality estimates
at some locations. It is concluded that the HadRM3 data are unsuitable for detailed (i.e. daily time step simulation model
based) site-specific impacts studies in their current form. However, the close similarity between modelled and observed data
for the historical case raises the potential for using simple adjustment methods and applying these to future projection data. 相似文献
135.
Chris Blake Russell J. Jurek Sarah Brough Matthew Colless Warrick Couch Scott Croom Tamara Davis Michael J. Drinkwater Duncan Forbes Karl Glazebrook Barry Madore Chris Martin Kevin Pimbblet Gregory B. Poole Michael Pracy Rob Sharp Todd Small David Woods 《Monthly notices of the Royal Astronomical Society》2009,395(1):240-254
136.
137.
E. K. J. Kilpua P. C. Liewer C. Farrugia J. G. Luhmann C. Möstl Y. Li Y. Liu B. J. Lynch C. T. Russell A. Vourlidas M. H. Acuna A. B. Galvin D. Larson J. A. Sauvaud 《Solar physics》2009,254(2):325-344
We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using
observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing
the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams
and magnetic clouds observed in the vicinity of the sector boundary. The observing satellites were separated by a longitudinal
distance comparable to the typical radial extent of magnetic clouds at 1 AU (fraction of an AU), and, indeed, clear differences
were evident in the records from these spacecraft. Two partial-halo coronal mass ejections (CMEs) were launched from the same
active region less than a day apart, the first on 19 May and the second on 20 May 2007. The clear signatures of the magnetic
cloud associated with the first CME were observed by STEREO B and Wind while only STEREO A recorded clear signatures of the magnetic cloud associated with the latter CME. Both magnetic clouds
appeared to have interacted strongly with the ambient solar wind and the data showed evidence that they were a part of the
coronal streamer belt. Wind and STEREO B also recorded a shocklike disturbance propagating inside a magnetic cloud that compressed the field and plasma
at the cloud’s trailing portion. The results illustrate how distant multisatellite observations can reveal the complex structure
of the extension of the coronal streamer into interplanetary space even during the solar activity minimum.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
138.
K. D. C. Simunac L. M. Kistler A. B. Galvin M. A. Lee M. A. Popecki C. Farrugia E. Moebius L. M. Blush P. Bochsler P. Wurz B. Klecker R. F. Wimmer-Schweingruber B. Thompson J. G. Luhmann C. T. Russell R. A. Howard 《Solar physics》2009,259(1-2):323-344
The heliocentric orbits of the two STEREO satellites are similar in radius and ecliptic latitude, with separation in longitude increasing by about 45° per year. This arrangement provides a unique opportunity to study the evolution of stream interfaces near 1 AU over time scales of hours to a few days, much less than the period of a Carrington rotation. Assuming nonevolving solar wind sources that corotate with the Sun, we calculated the expected time and longitude of arrival of stream interfaces at the Ahead observatory based on the in situ solar wind speeds measured at the Behind observatory. We find agreement to within 5° between the expected and actual arrival longitude until the spacecraft are separated by more than 20° in heliocentric inertial longitude. This corresponds to about one day between the measurement times. Much larger deviations, up to 25° in longitude, are observed after 20° separation. Some of the deviations can be explained by a latitude difference between the spacecraft, but other deviations most likely result from evolution of the source region. Both remote and in situ measurements show that changes at the source boundary can occur on a time scale much shorter than one solar rotation. In 32 of 41 cases, the interface was observed earlier than expected at STEREO/Ahead. 相似文献
139.
140.
M.R. Balme A. Pathare S.M. Metzger M.C. Towner S.R. Lewis A. Spiga L.K. Fenton N.O. Renno H.M. Elliott F.A. Saca T.I. Michaels P. Russell J. Verdasca 《Icarus》2012,221(2):632-645
Dust devils – convective vortices made visible by the dust and debris they entrain – are common in arid environments and have been observed on Earth and Mars. Martian dust devils have been identified both in images taken at the surface and in remote sensing observations from orbiting spacecraft. Observations from landing craft and orbiting instruments have allowed the dust devil translational forward motion (ground velocity) to be calculated, but it is unclear how these velocities relate to the local ambient wind conditions, for (i) only model wind speeds are generally available for Mars, and (ii) on Earth only anecdotal evidence exists that compares dust devil ground velocity with ambient wind velocity. If dust devil ground velocity can be reliably correlated to the ambient wind regime, observations of dust devils could provide a proxy for wind speed and direction measurements on Mars. Hence, dust devil ground velocities could be used to probe the circulation of the martian boundary layer and help constrain climate models or assess the safety of future landing sites.We present results from a field study of terrestrial dust devils performed in the southwest USA in which we measured dust devil horizontal velocity as a function of ambient wind velocity. We acquired stereo images of more than a 100 active dust devils and recorded multiple size and position measurements for each dust devil. We used these data to calculate dust devil translational velocity. The dust devils were within a study area bounded by 10 m high meteorology towers such that dust devil speed and direction could be correlated with the local ambient wind speed and direction measurements.Daily (10:00–16:00 local time) and 2-h averaged dust devil ground speeds correlate well with ambient wind speeds averaged over the same period. Unsurprisingly, individual measurements of dust devil ground speed match instantaneous measurements of ambient wind speed more poorly; a 20-min smoothing window applied to the ambient wind speed data improves the correlation. In general, dust devils travel 10–20% faster than ambient wind speed measured at 10 m height, suggesting that their ground speeds are representative of the boundary layer winds a few tens of meters above ground level. Dust devil ground motion direction closely matches the measured ambient wind direction.The link between ambient winds and dust devil ground velocity demonstrated here suggests that a similar one should apply on Mars. Determining the details of the martian relationship between dust devil ground velocity and ambient wind velocity might require new in situ or modelling studies but, if completed successfully, would provide a quantitative means of measuring wind velocities on Mars that would otherwise be impossible to obtain. 相似文献