Influence of Anamalous Eurasian Spring Snow Cover on the Indian Summer Monsoon

有强有力的经验证据表明，欧亚大陆春季积雪面积与随后的夏季降雨量与印度降雨量呈负相关。本研究的目的是通过对大气环流模型（GCM）的一系列实验来研究这种经验关系的有效性。GCM是一种在水平分辨率为40波数、垂直分辨率为18层的菱形截断的全球光谱模式。物理过程包括：地表生物物理过程、日循环、浅对流和深对流、云辐射相互作用以及大尺度和亚网格尺度地形的影响。提出了欧亚大陆春季不同积雪面积和深度对夏季风环流影响的三个试验。这三个实验将模拟从3月1日到9月30日的年循环模式下的整体全球环流。这些模拟的差异仅仅是由于3月1日欧亚大陆上规定的积雪范围和深度。所有其他规定的数量将来自气候学。第一个实验是通过规定一个类似于1970年春季观测到的最小雪量来确定雪量负异常对季风环流的影响。在这个实验中，PI将使用平均雪深。第二次和第三次试验的目的是研究与1972年春季观测到的积雪范围正异常的影响。在第二个实验中，为了隔离地表反照率的影响，PI规定了最小雪深。在第三个实验中，他将规定一个最大降雪量，以研究反照率的影响以及融化和蒸发的影响。这些异常实验的结果将与控制模拟的结果进行比较，以检验这些结果的统计意义。这项研究很重要，因为它旨在提高我们对气候系统重要组成部分、地面边界强迫和季风之间关系的理解。

There is strong empirical evidence that the areal extent of Eurasian spring snow cover is negatively correlated with the following summer rainfall over rainfall over India. The purpose of this research is to study the validity of this empirical relationship from a series of experiments with a general circulation model (GCM). The GCM is a global spectral model with rhomboidal truncation at wave number 40 horizontal resolution with 18 layers in the vertical. The physical processes include: surface biophysical processes, diurnal cycle, shallow and deep convection, cloud-radiation interaction and effects of large-scale and subgrid- scale orography. Three experiments are proposed with varying areal extent and depth of the Eurasian snow cover in the spring to study its influence on the summer monsoon circulations. All three experiments will simulate ensemble global circulations in an annual cycle mode from March 1 though September 30. The difference in these simulations are only due to the prescribed snow extent and depth over Eurasia on March 1. All other prescribed quantities will come from climatology. The first experiment is to determine the impact of a negative anomaly in the snow extent on the monsoon circulations by prescribing a minimum snow extent similar to that observed during the spring of 1970. In this experiment the PI will use average snow depth. The second and third experiments are designed to investigate the impact of a positive anomaly in the snow extent similar to that observed during the spring of 1972. In the second experiment the PI prescribe a minimum snow depth in order to isolate the effects of the surface albedo. In the third experiment he will prescribe a maximum snow in order to study the effects of albedo as well as the effects of melting and evaporation. The results of these anomaly experiments will be compared with the control simulations to test the statistical significance of these results..This research is important because it seeks to improve our understanding of relationships between important components of the climate system, surface boundary forcing and monsoons.