Variability and Changes in Rainfall Observed Across Jharkhand Region (India)

Rainfall variability has a substantial impact on water supplies, agricultural output, and, as a result, the economy. It examines the historical spatiotemporal variability and trend of rainfall on Jharkhand's annual and seasonal time series state over a 60-year period (1954–2013). The goal of this study was to find trends in long and short-term changes in rainfall amounts in the Jharkhand region at various spatial scales. With the help of the wavelet technique, we were able to determine the periodicity of rainfall over time and identify active and break days in the monsoon season. When the OLR positive anomaly increases, rainfall decreases (Break days), and when the OLR negative anomaly increases, rainfall increases (Active days). The Indian summer monsoon extreme is also strongly linked to the Equatorial Indian Ocean Oscillation (EQUINOO), which is based on surface zonal wind across the central equatorial Indian Ocean. Because the Bay of Bengal is next to Jharkhand, local disturbances or cyclonic events are also discovered and their impact on rainfall is investigated. Keywords: Rainfall, ENSO, Wavelet Transform, Active and Break days, Cyclone, Climate Change.

Equatorial atmospheric zonal circulation changes over India Ocean during recent decades

<p>The equatorial zonal asymmetric (Walker) circulation causes changes in the tropical rainfall pattern which induces devastation flood and drought that considerably impact the lives of millions of people. However, understanding of changes in zonal circulation is not yet certain. Here we examine the robustness of changes in Indian Walker Circulation (IWC) characteristics using different reanalysis and observation datasets in terms of the linear trends of IWC. The meridional (5<sup>o</sup>S:5<sup>o</sup>N)  averaged vertical velocity using different datasets are used to precisely locate the ascending (94<sup>o</sup>E:104<sup>o</sup>E, eastern) and descending (35<sup>o</sup>E:45<sup>o</sup>E, western) branch of IWC. We analyzed the zonal sea level pressure (SLP) gradient, velocity potential (VP) at 850 and 200 hPa, surface zonal wind (SZW) and zonal mass stream function (ZMSF) anomalies over the period of 1980–2017. We found that the magnitude of ZMSF representing anticlockwise circulation has an increasing trend in all the datasets. This kind of change is physically in agreement with the changes of SLP and SZW (an increasing trend in westerlies over the central IO) while the VP shows the decreasing trend which is in agreement with the strengthening of IWC during the recent decades. JRA55 is the most reliable which shows the significant and highest trend among all other datasets. The change point detection using the Pettitt method is applied to the normalized mean of all datasets which determines that in the post-1997-98 there is a significant strengthening of IWC as compared to the pre-1997-98 which demonstrates that IWC is highly sensitive by super El-Nino. The attribution of this strengthening can be examined using the CMIP5/6 datasets to determine the relative contribution of anthropogenic warming and natural variability.</p>

Seasonal Dependence of the MJO–ENSO Relationship

Observations of the development of recent El Niño events suggest a pivotal role for the Madden–Julian oscillation (MJO). Previous attempts to uncover a systematic relationship between MJO activity and the El Niño–Southern Oscillation (ENSO), however, have yielded conflicting results. In this study the MJO–ENSO relationship is stratified by season, and the focus is on MJO activity in the equatorial western Pacific. The results demonstrate that MJO activity in late boreal spring leads El Niño in the subsequent autumn–winter for the period 1979–2005. Spring is the season when MJO activity is least asymmetric with respect to the equator and displays the most sensitivity to SST variations at the eastern edge of the warm pool. Enhanced MJO activity in the western Pacific in spring is associated with an eastward-expanded warm pool and low-frequency westerly surface zonal wind anomalies. These sustained westerly anomalies in the western Pacific are hypothesized to project favorably onto a developing El Niño in spring.