Trend analysis of rainfall is often carried out in water resources management to understand its distribution over a given region. The cumulative seasonal and annual rainfall derived from monthly datasets spanning 102 years (1901–2002) for 11 districts of the semi-arid Karnataka, India, was used for the trend analysis. The two-step homogeneous test approach was carried out on all the time series. Then, lag-1 autocorrelation was conducted only on homogeneous time series. Only 78.18 % of the total time series data were detected as homogeneous, and 95.35% of time series data were found to have insignificant autocorrelation. Then, the Innovative Trend Analysis (ITA) method was applied to 43 homogeneous rainfall time series, as well as to 41 time series using the MK and SR tests, and to two time series using the mMK test. The MK and SR tests detected a significant trend in 14.63% of the time series, while the ITA method was able to detect a trend in 93.02% of the total time series data. The MK and SR tests revealed significant trends in winter and post-monsoon season precipitation for two districts, but only for one district in the case of summer and annual rainfall. No trend was identified for monsoon season precipitation. The mMK test showed a positive trend for the post-monsoon season in a district, while the ITA method revealed significant trends for all seasons in most districts. The sub-trend analysis revealed trends that traditional methods were unable to detect.
Annual and seasonal trends in actual evapotranspiration over different meteorological sub-divisions in India using satellite-based data
- विवरण.
- श्रेणी:Publications.
by Raghavendra Prasad K, Kantha Rao Bhimala, G. K. Patra, Himesh S & Sheshakumar Goroshi
The present study analyzed the actual evapotranspiration (ETa) and its components [transpiration (Et), bare soil evaporation (Eb), interception loss (Ei), and open water evaporation (Eo)] data to study the long-term (1980–2018) trends over different meteorological sub-divisions in India. Quantitatively, all India average (µ) annual ETa is 573 mm (standard deviation (σ) = 29 mm), where Et (µ = 456 mm; σ = 30 mm) plays a major role compared to other evaporation processes like Eb (µ = 56 mm; σ = 9 mm), Ei (µ = 34 mm; σ = 3 mm), and Eo (µ = 27 mm). The Mann–Kendall (MK) test reveals an increasing trend (1.33 mm/yr) in annual ETa due to the rising trend in Et (1.91 mm/yr) and Ei (0.16 mm/yr). The sub-division-wise analysis shows the increasing trend in ETa observed over irrigated regions located in the south, north-west, and foothills of the Himalayas during pre-monsoon (March–May) and monsoon season (June–September). The correlation analysis observed a complex relationship between ETa and climatic factors (rainfall (RF), soil moisture (SM), surface temperature (T), relative humidity (RH), surface net solar radiation (SSR), and wind speed (WS)) during monsoon season such that the water-limited areas have a positive correlation with SM, RH and RF, and negative correlation with WS, T, and SSR, whereas, in energy-limited areas (east India), the ETa showed a positive correlation with SSR and T and negative correlation with RF. The main climatic drivers for the increasing trend of ETa are SM and rainfall over dry regions and SSR and T over densely vegetated regions in India.
