scholarly journals Observed Relationship of Spring and Summer East Asian Rainfall with Winter and Spring Eurasian Snow

2007 ◽  
Vol 20 (7) ◽  
pp. 1285-1304 ◽  
Author(s):  
Renguang Wu ◽  
Ben P. Kirtman
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Snow Water Equivalent ◽  
Southern Oscillation ◽  
Southern China ◽  
Summer Rainfall ◽  
Wave Pattern ◽  
Summer Monsoon Rainfall ◽  
The Tibetan Plateau

Abstract This study investigates the relationship between spring and summer rainfall in East Asia and the preceding winter and spring snow cover/depth over Eurasia, using station rainfall observations, satellite-observed snow cover, satellite-derived snow water equivalent, and station observations of the number of days of snow cover and snow depth. Correlation analysis shows that snow-depth anomalies can persist from winter to spring whereas snow cover anomalies cannot in most regions of Eurasia. Locally, snow cover and snow-depth anomalies in February are not related in most regions to the north of 50°N, but those anomalies in April display consistent year-to-year variations. The results suggest that the winter snow cover cannot properly represent all the effects of snow and it is necessary to separate the winter and spring snow cover in addressing the snow–monsoon relationship. Spring snow cover in western Siberia is positively correlated with spring rainfall in southern China. The circulation anomalies associated with the western Siberian spring snow cover variations show an apparent wave pattern over the eastern Atlantic through Europe and midlatitude Asia. Spring snow cover over the Tibetan Plateau shows a moderate positive correlation with spring rainfall in southern China. Analysis shows that this correlation includes El Niño–Southern Oscillation (ENSO) effects. In contrast to the Indian summer monsoon rainfall for which the ENSO interferes with the snow effects, the Tibetan Plateau snow cover and ENSO work cooperatively to enhance spring rainfall anomalies in southern China. In comparison, ENSO has larger impacts than the snow on spring rainfall in southern China.

Trends in Summer Rainfall over China Associated with the Tibetan Plateau Sensible Heat Source during 1980–2008

2013 ◽  
Vol 26 (1) ◽  
pp. 261-275 ◽  
Author(s):  
Anmin Duan ◽  
Meirong Wang ◽  
Yonghui Lei ◽  
Yangfan Cui
Keyword(s):  
Tibetan Plateau ◽  
Heat Source ◽  
Snow Depth ◽  
Southern China ◽  
Summer Rainfall ◽  
Monsoon Circulation ◽  
The Tibetan Plateau ◽  
Sensible Heat ◽  
Local Circulation ◽  
Precipitation Events

Abstract The impacts of the thermal forcing over the Tibetan Plateau (TP) in spring on changes in summer rainfall in China are investigated using historical records from the period between 1980 and 2008. The spring sensible heat (SH) flux and snow depth over the TP both decreased over this time period, although the trend in SH was more significant than that in snow depth. The similarity between patterns of precipitation trends over China and corresponding patterns of regression coefficients on the leading mode of spring SH change over the TP demonstrates the distinct contribution of changes in TP SH during spring. Enhanced precipitation in southern China was accompanied by increases in heavy rainfall, precipitation intensity, and the frequency of precipitation events, while reduced precipitation in northern China and northeastern China was primarily associated with decreases in the frequency of precipitation events. Further analysis using observational data and numerical simulations reveals that the reductions in SH over the TP have weakened the monsoon circulation and postponed the seasonal reversal of the land–sea thermal contrast in East Asia. In addition, the positive spring SH anomaly may generate a stronger summer atmospheric heat source over the TP due to the positive feedback between diabatic heating and local circulation.

scholarly journals Impact of Solar Activity on Snow Cover Variation Over the Tibetan Plateau and Linkage to the Summer Precipitation in China

2022 ◽  
Vol 9 ◽  
Author(s):  
Yan Song ◽  
Zhicai Li ◽  
Yu Gu ◽  
Ziniu Xiao
Keyword(s):  
Solar Activity ◽  
Tibetan Plateau ◽  
Snow Cover ◽  
Time Scales ◽  
Southern Oscillation ◽  
Summer Precipitation ◽  
Summer Rainfall ◽  
High Solar Activity ◽  
The Tibetan Plateau ◽  
The Impact

Solar activity is one of the main external forcing factors driving the Earth’s climate system to change. The snow cover over the Tibetan Plateau is an important physical factor affecting the East Asian climate. At present, insufficient research on the connection between solar activity and snow cover over the Tibetan Plateau has been carried out. Using Solar Radio Flux (SRF), Solar Sunspot Number (SSN), and Total Solar Irradiance (TSI) data, this paper calculated the correlation coefficients with snow indices over the Tibetan Plateau, such as winter and spring snow depth (WSD/SSD) and snow day number (WSDN/SSDN). These snow indices are obtained from the daily gauge snow data in the Tibetan Plateau. Through correlation analyses, it is found that there are significant synchronous or lag correlations between snow indices and solar parameters on multi-time scales. In particular, the Spring Snow Day Number (SSDN) is of significant synchronous or lag correlation with SRF, SSN, and TSI on multi-time scales. It is further found that SSDN over the Tibetan Plateau has more stable positive correlations with SRF by using the 21-year running mean and cross spectrum analyses. Therefore, SSDN can be ascertained to be the most sensitive snow index to the solar activity compared with other snow indices. Moreover, its influence on summer precipitation of China is strongly regulated by solar activity. In high solar activity years (HSAY), the significant correlated area of summer precipitation in China to SSDN is located further north than that in low solar activity years (LSAY). Such impact by solar activity is also remarkable after excluding the impact of ENSO (i.e., El Niño–Southern Oscillation) events. These results provide support for the application of snow indices in summer rainfall prediction in China.

scholarly journals Spatio-Temporal Variation Characteristics of Snow Depth and Snow Cover Days over the Tibetan Plateau

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 307
Author(s):  
Chi Zhang ◽  
Naixia Mou ◽  
Jiqiang Niu ◽  
Lingxian Zhang ◽  
Feng Liu
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Feedback Effect ◽  
Effect Of Temperature ◽  
The Tibetan Plateau ◽  
Reanalysis Dataset ◽  
Spatio Temporal ◽  
The Impact ◽  
Main Factor

Changes in snow cover over the Tibetan Plateau (TP) have a significant impact on agriculture, hydrology, and ecological environment of surrounding areas. This study investigates the spatio-temporal pattern of snow depth (SD) and snow cover days (SCD), as well as the impact of temperature and precipitation on snow cover over TP from 1979 to 2018 by using the ERA5 reanalysis dataset, and uses the Mann–Kendall test for significance. The results indicate that (1) the average annual SD and SCD in the southern and western edge areas of TP are relatively high, reaching 10 cm and 120 d or more, respectively. (2) In the past 40 years, SD (s = 0.04 cm decade−1, p = 0.81) and SCD (s = −2.3 d decade−1, p = 0.10) over TP did not change significantly. (3) The positive feedback effect of precipitation is the main factor affecting SD, while the negative feedback effect of temperature is the main factor affecting SCD. This study improves the understanding of snow cover change and is conducive to the further study of climate change on TP.

Improved Simulation of the East Asian Summer Monsoon Rainfall with Satellite-Derived Snow Water Equivalent Data*

2009 ◽  
Vol 137 (6) ◽  
pp. 1790-1804 ◽  
Author(s):  
Kazuyoshi Souma ◽  
Yuqing Wang
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Snow Water Equivalent ◽  
Asian Summer Monsoon ◽  
Lower Troposphere ◽  
Seasonal Prediction ◽  
Summer Monsoon Rainfall ◽  
Early Summer ◽  
Shortwave Radiation ◽  
The Tibetan Plateau

Abstract The effect of Eurasian spring snow amount on the summer monsoon rainfall over East Asia has been studied both observationally and numerically. The results indicate that the Eurasian spring snow amount could be important for seasonal prediction of East Asian summer monsoon (EASM) rainfall. Therefore, accurately initializing snow could be critical to improving seasonal prediction of EASM rainfall by numerical models. An attempt has been made in this study to initialize snow in a regional climate model using snow water equivalent (SWE) data derived from a microwave imager. Results from an ensemble seasonal prediction experiment for the 2005 EASM show that the satellite-derived SWE data can be effectively used to initialize a dynamical seasonal prediction model, which leads to improved seasonal prediction of EASM rainfall. Possible effects of snow anomalies over the Tibetan Plateau on EASM rainfall were also studied through a comparative ensemble simulation in which snow was initialized by spinning up the same model from the previous winter. It is found that the anomalous snow amount over the Tibetan Plateau could lead to cooling of the surface and lower troposphere not only over the Tibetan Plateau but also in the surrounding areas because of the reduced net surface shortwave radiation associated with the high snow albedo. This would result in positive anomalies in geopotential height and weaken the cyclonic monsoon circulation in the lower troposphere in East Asia, causing a rainfall increase in South China but a reduction in the Yangtze River Valley in early summer (May–June). The difference in rainfall in midsummer (July–August) was not significant when compared with that in early summer. The surface heat budget indicates that the reduced net surface shortwave radiation is largely balanced by the reduced surface sensible heat flux.

scholarly journals Modeled Northern Hemisphere Autumn and Winter Climate Responses to Realistic Tibetan Plateau and Mongolia Snow Anomalies

2017 ◽  
Vol 30 (23) ◽  
pp. 9435-9454 ◽  
Author(s):  
Shizuo Liu ◽  
Qigang Wu ◽  
Xuejuan Ren ◽  
Yonghong Yao ◽  
Steven R. Schroeder ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Water Equivalent ◽  
Feedback Mechanism ◽  
The Tibetan Plateau ◽  
Surface Cooling ◽  
Sea Ice Extent ◽  
Winter Climate ◽  
Snow Cover Extent ◽  
Autumn And Winter

Observational studies link a persistent dipole of autumn and winter snow cover anomalies over the Tibetan Plateau (TP) and Mongolia with winter Pacific–North American (PNA)-like atmospheric variations. This study investigates atmospheric responses to such snow forcings using multiple ensemble transient integrations of the CAM4 and CLM4.0 models. Model boundary conditions are based on climatological sea ice extent and sea surface temperature, and satellite observations of snow cover extent (SCE) and snow water equivalent (SWE) over the TP and Mongolia from October to March in 1997/98 (heavy TP and light Mongolia snow) and 1984/85 (light TP and heavy Mongolia snow), with model-derived SCE and SWE elsewhere. In various forcing experiments, the ensemble-mean difference between simulations with these two extreme snow states identifies local, distant, concurrent, and delayed climatic responses. The main atmospheric responses to a dipole of high TP and low Mongolia SCE persisting from October to March (versus the opposite extreme) are strong TP surface cooling, warming in the surrounding China and Mongolia region, and a winter positive PNA-like response. The localized response is maintained by persistent diabatic cooling or heating, and the remote PNA response results mainly from the increased horizontal eastward propagation of stationary Rossby wave energy due to persistent TP snow forcing and also a winter transient eddy feedback mechanism. With a less persistent dipole anomaly in autumn or winter only, local responses are similar depending on the specific anomalies, but the winter PNA-like response is nearly absent or noticeably reduced.

scholarly journals Evaluation of snow depth and snow cover over the Tibetan Plateau in global reanalyses using in situ and satellite remote sensing observations

2019 ◽  
Vol 13 (8) ◽  
pp. 2221-2239 ◽  
Author(s):  
Yvan Orsolini ◽  
Martin Wegmann ◽  
Emanuel Dutra ◽  
Boqi Liu ◽  
Gianpaolo Balsamo ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Operating Conditions ◽  
The Tibetan Plateau ◽  
Critical Surface ◽  
High Altitudes ◽  
Medium Range ◽  
In Situ Observations

Abstract. The Tibetan Plateau (TP) region, often referred to as the Third Pole, is the world's highest plateau and exerts a considerable influence on regional and global climate. The state of the snowpack over the TP is a major research focus due to its great impact on the headwaters of a dozen major Asian rivers. While many studies have attempted to validate atmospheric reanalyses over the TP area in terms of temperature or precipitation, there have been – remarkably – no studies aimed at systematically comparing the snow depth or snow cover in global reanalyses with satellite and in situ data. Yet, snow in reanalyses provides critical surface information for forecast systems from the medium to sub-seasonal timescales. Here, snow depth and snow cover from four recent global reanalysis products, namely the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 and ERA-Interim reanalyses, the Japanese 55-year Reanalysis (JRA-55) and the NASA Modern-Era Retrospective analysis for Research and Applications (MERRA-2), are inter-compared over the TP region. The reanalyses are evaluated against a set of 33 in situ station observations, as well as against the Interactive Multisensor Snow and Ice Mapping System (IMS) snow cover and a satellite microwave snow depth dataset. The high temporal correlation coefficient (0.78) between the IMS snow cover and the in situ observations provides confidence in the station data despite the relative paucity of in situ measurement sites and the harsh operating conditions. While several reanalyses show a systematic overestimation of the snow depth or snow cover, the reanalyses that assimilate local in situ observations or IMS snow cover are better capable of representing the shallow, transient snowpack over the TP region. The latter point is clearly demonstrated by examining the family of reanalyses from the ECMWF, of which only the older ERA-Interim assimilated IMS snow cover at high altitudes, while ERA5 did not consider IMS snow cover for high altitudes. We further tested the sensitivity of the ERA5-Land model in offline experiments, assessing the impact of blown snow sublimation, snow cover to snow depth conversion and, more importantly, excessive snowfall. These results suggest that excessive snowfall might be the primary factor for the large overestimation of snow depth and cover in ERA5 reanalysis. Pending a solution for this common model precipitation bias over the Himalayas and the TP, future snow reanalyses that optimally combine the use of satellite snow cover and in situ snow depth observations in the assimilation and analysis cycles have the potential to improve medium-range to sub-seasonal forecasts for water resources applications.

An interdecadal change in the influence of ENSO on the spring Tibetan Plateau snow cover variability in the early 2000s

2021 ◽  
pp. 1
Author(s):  
Zhibiao Wang ◽  
Renguang Wu ◽  
Song Yang ◽  
Mengmeng Lu
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Interdecadal Change ◽  
The Tibetan Plateau ◽  
The Relationship ◽  
Tibetan Plateau Snow Cover ◽  
Sst Anomalies

AbstractEl Niño–Southern Oscillation (ENSO) and the Tibetan Plateau snow cover are important factors in interannual climate variability. The relationship between ENSO and the Tibetan Plateau snow variation is still an issue unresolved. While some studies suggested that ENSO is a key factor of changes in snow cover over the Tibetan Plateau, other studies noted independence between the two. The present study revealed a prominent interdecadal change in the relationship between ENSO and the spring Tibetan Plateau snow cover variation in the early 2000s. There is a significant positive correlation between ENSO and the spring Tibetan Plateau snow cover variation in the period 1988-2003, but an obvious negative relationship is detected in the period 2004-2019. The interdecadal change in the ENSO-snow relationship is related to the distinct pathway of ENSO influence on the spring Tibetan Plateau snow cover variation during the two periods. In the period 1988-2003, ENSO induces anomalous convection over the tropical western North Pacific that in turn cause atmospheric circulation and moisture anomalies over the Tibetan Plateau. The resultant winter snow anomalies over the central-eastern Tibetan Plateau persist to the following spring. In the period 2004-2019, ENSO induces North Atlantic sea surface temperature (SST) anomalies in winter that are maintained to the following spring. The North Atlantic SST anomalies then stimulate the atmospheric circulation anomalies extending to the Tibetan Plateau that induce snow cover anomalies there in spring. The different processes of ENSO influence lead to opposite anomalies of spring snow cover over the Tibetan Plateau in the two periods.

scholarly journals Snow cover variations across China from 1951–2018

2020 ◽  
Author(s):  
Xiaodong Huang ◽  
Changyu Liu ◽  
Zhaojun Zheng ◽  
Yunlong Wang ◽  
Xubing Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Northeast China ◽  
Regional Differences ◽  
Meteorological Factors ◽  
Onset Date ◽  
The Tibetan Plateau ◽  
Maximum Snow Depth ◽  
The Postponement

Abstract. Based on a snow depth dataset retrieved from meteorological stations, this experiment explored snow indices, including snow depth (SD), snow covered days (SCDs), and snow phenology variations, across China from 1951 to 2018. The results indicated that the snow cover in China exhibits regional differences. The annual mean SD tended to increase, and the increases in mean and maximum snow depth were 0.04 cm and 0.1 cm per decade, respectively. SCDs tended to increase by approximately 0.5 days per decade. The significant increases were concentrated at latitudes higher than 40° N, especially in Northeast China. However, in the Tibetan Plateau, the SD and SCDs tended to decrease but not significantly. Regarding the snow phenology variations, the snow duration days in China decreased, and 25.2 % of the meteorological stations showed significant decreasing trends. This result was mainly caused by the postponement of the snow onset date and the advancement of the snow end date. Geographical and meteorological factors are closely related to snow cover, especially the change in temperature, which will lead to significant changes in snow depth and phenology.

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