Trend analysis and forecast of pre-monsoon rainfall over India

Abstract

Pre‐monsoon (March, April and May ‐ MAM) rainfall over India is highly variable. A pre‐whitened Mann‐Kendall test was used to investigate trends in rainfall during MAM. The results indicate the presence of a significant (at the 10% level) increasing trend at four stations (Ajmer, Bikaner, Indore and Kolkata), out of which two stations (Ajmer and Bikaner) show a statistically significant increasing trend. A decreasing trend is observed at two stations (Belgaum and Minicoy). Practical significance was also explored in terms of percentage changes, using the Theil‐Sen median slope estimator. Forecasts made using a univariate autoregressive integrated moving average (ARIMA) model for MAM indicate that there has been a significant rise in the pre‐monsoon rainfall over the northwestern part of India.

Role of MJO in modulating rainfall characteristics observed over India in all seasons utilizing TRMM

“…The pre‐monsoonal season is characterized by very high insolation over land, resulting in the formation of strong low and opposing high‐pressure systems over adjacent oceans (Kothawale et al ., ; Tyagi et al ., ). Reports suggest an increasing trend in pre‐monsoon rainfall over various Indian sub‐regions (Kumar et al ., ; Sathiyamoorthy et al ., ; Narayanan et al ., ). During this season Bangladesh, Gangetic West Bengal and northeast India receives the highest amount of rainfall (∼30% of annual totals or ∼100 cm).…”

“…Reports suggest an increasing trend in pre-monsoon rainfall over various Indian sub-regions Sathiyamoorthy et al, 2010;Narayanan et al, 2016). During this season Bangladesh, Gangetic West Bengal and northeast India receives the highest amount of rainfall (∼30% of annual totals or ∼100 cm).…”

“…In particular, greater research into rainfall dynamics associated with 'active' and 'break' phases of the monsoon is required -albeit that some recent studies have helped to address this gap (Mishra et al, 2016). As trend analyses reveal that ISM rainfall has been decreasing, while for other seasons an increasing trend is observed, the need to understand regional drivers is greater than ever Narayanan et al, 2016).…”

Ongoing Conflict Makes Yemen Dark: From the Perspective of Nighttime Light

“…The Theil-Sen Median is a robust trend analysis method with non-parametric statistics [49] and is a particularly effective tool for estimating the trends in small series [49,50]. The Theil-Sen Median has been widely used to test the trend of time series remote sensing images [51][52][53], especially in long time series of vegetation variation analysis [49,50,52]. The formula is as follows:…”

“…sensing images [51][52][53], especially in long time series of vegetation variation analysis [49,50,52]. The formula is as follows:…”