气候学家如何定义“开始”的雨季在单峰季风气候?- 江南体育网页版- - - - -地球科学堆江南电子竞技平台栈交换 最近30从www.hoelymoley.com 2023 - 07 - 11 - t09:31:09z //www.hoelymoley.com/feeds/question/1062 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/1062 14 气候学家如何定义“开始”的雨季在单峰季风气候? generic_user //www.hoelymoley.com/users/545 2014 - 06 - 01 - t18:57:17z 2017 - 06 - 20 - t13:34:03z < p >的gridcell, 500毫米和800毫米降雨量等降雨量线在撒哈拉以南非洲,我有dekadal降雨(从饥荒预警系统)。他们相当分散到大陆,其中有很多,所以他们会有不同的季节性,尽管他们都应该大致单峰(尤其是我的纬度)。< / p > < p >我想定义一个算法来定义平均雨季的开始和结束。到目前为止,我想以下几点:为每个gridcell < / p > < p >: < / p > < ol > <李>定义的月平均最大降雨量李< / > <李>找到月平均最大降雨量月前减少3落后的月平均降雨量的总和,当月需包含至少20%的年降雨量。它定义为平均开始。李李< / > < >后找到月平均最大降雨量月做同样的事,只有3月平均降雨量的滞后。定义月雨季的结束。< /李> < / ol > < p > 20%这个数字看似随意,但我不确定该做些什么。我不是一个气候科学家,虽然也许我可以玩一个在电视上。有一个公认的惯例吗? If not, any suggestions on improving my algorithm?

//www.hoelymoley.com/questions/1062/-/10645 # 10645 3 她回答的气候学家如何定义“开始”的雨季在单峰季风气候? //www.hoelymoley.com/users/8396 2017 - 06 - 20 - t13:34:03z 2017 - 06 - 20 - t13:34:03z < p >我发现下面的方法非常简单和优雅。也许我可以说服你考虑。< / p >

For the South American (SA) monsoon, Silva et al. (2007) and Carvalho et al. (2012) proposed the Long-scale South American Monsoon Index (LISAM), based on the annual cycle of some fields.

For the 2012 paper, where several precipitation datasets are used to calculate what you want, the methodology is as follows:

  1. Compute the empirical orthogonal function (EOF) of a precipitation gridded data on land over SA. (There are some details as weigth by latitude, you may want to do combined EOF etc etc... but the essence of the idea is the same). Note that EOF is computed on raw precipitation, not anomalies.

  2. The first EOF represents the annual (seasonal) cycle of the monsoon. The First PC (PC1) shows it clearly (Figure 2 in Silva et al. 2007)

At last, having the time series of PC1, you can determine:

Start (onset): the day in which PC1 turns positive. End (demise): the day in which PC1 turns negative.

Further detailes are given in the cited papers. Hope it helps.

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