| Drought is a complex phenomenon of environmental processes and considered as the stochastic nature of hazards with a prolonged scarcity and dearth character that results from the meager annual precipitation and superficial water contents.Drought is a prolonged event of insufficient rainfall with follow-on extensive damage to crops,resulting in loss of yield.The drought has always impacted the agricultural,meteorological,ecological and socio-economic with potentially significant consequences.The global warming causes the global climate changes,and Pakistan listed in number eight of the most affected ten countries from 1995-2014 in the world.The natural disasters in response to drought and flood are the most common and frequently occurring hazards in Pakistan over a recent couple of century due to environmental,climatic and ecosystem anthropogenic factors.Droughts and floods are the world's costliest natural disasters due to extreme climate events under global warming conditions.This is obvious to investigate the agricultural drought conditions in the region,as the soil moisture had a significant role in retains of dry and wet spells in both rain-fed and irrigated conditions and the key indicator of drought and flood.This study determines the multi-years drought conditions as well as the warm edges(LSTmax)and cold edges(LSTmin)in response to soil moisture during 2003-2014 over the cropland of Punjab,Pakistan.This learning employed the Spacebome EOS's Moderate Resolution Imaging Spectroradiometer(MODIS)data products to acquire the land surface conditions during the winter wheat crop season in the cropland of the plain under rain-fed and irrigated conditions.The employed near-real-time drought monitoring approach termed as vegetation temperature condition index(VTCI)integrate the normalized difference vegetation index(NDVI)and land surface temperature(LST)to determine the warm and cold edges as well as to investigate dry and wet conditions vigorously.The VTCI feature plots reside in LST-NDVI space is the most appropriate method for the determination of VTCI imagery as well as warm and cold edges in response to soil moisture.The geospatial near-real-time coupling(NRTC)approach,which utilizes the VTCI time series values and daily precipitation data,was used for the validation of dry and wet spell at five weather-stations in the plain of Punjab.Variations in warm and cold edges expose the drought conditions due to weather extreme's uneven temperature from winter into summer.The spatial and temporal observations of the VTCI imagery in the specified periods present the dry and wet conditions due to temporal changes of the land surface soil moisture conditions and demonstrate the irregular retreat states of edges for the agricultural practices which depend on the location and season in the region.The VTCI drought monitoring approach is categorized and offers with normality or wetness(1.00-0.57),mild drought(0.56-0.44),moderate drought(0.43-0.38)and severe drought(0.37-0.00).The VTCI time series generalized characteristics of the drought exhibit the plain with respective weather-stations in three climate zones(south,center,and northeast).The south and center of the plain with low accumulative precipitation results insignificant VTCI values,whereas,in the northeast with adequate precipitation results in significant VTCI values.Even though the Plain had the best-irrigated system but the temporal and spatial observations reveal that the south and center of the plain expose to drought in contrast to the northeast with high occurrences of drought,whereas,the northeast indicates most of the normal conditions of drought in the plain.The VTCI spatial and temporal observations in the region during the 12-yr period represent mostly significant drought conditions in the northeast in contrast to centre and south with insignificant drought conditions for the winter wheat crop seasons in the year of 2004,2006,2008,2010 and 2011 during 2003 to 2014 under both rainfed and irrigated conditions in the region.During the 12-yr drought periods of winter wheat crop seasons in the year of 2004,2006,2008,2010 and 2011 the decreased was calculated with 2500,2588,2438,2846 and 2737 yield per hectare in KG's from the average yield production under both rainfed and irrigated conditions in the region.Before and after the flood inception the wheat crop area was 6691.0 hectares in 2010-2011,whereas,in 2011-2012 it was decreased to 6482.9 hectares.This shows that the flood(2010)affects the area and the production,and was decreased from 19.041 to 17.7389 million tonnes.With abovementioned drought and yield calculations,illustrates the insufficient irrigated practices in the plain and shows reliance on the seasonal rainfall during the winter wheat crop season in the plain of Punjab.The VTCl time series indicates that the south and center of the plain shows lower VTCI values,due to the lack of rainfall,whereas,in the northeast had high VTCI values with adequate rainfall at five weather-stations,and present a better response to recent precipitation.The VTCI time series values at pixel area of 1 km resolution at five weather stations illustrate that the plain of Punjab is not only dependent on irrigated practices but also dependent on rainfall.The study exhibit the temporal changes of the land surface drought conditions through the periods of 16-day to 12-month accumulative precipitation had a significant correlation with the VTCI time series values,varies with four periods(2003-2008,2010,2011-2014,2003-2014)at five weather-stations during 2003-2014.The relationship between VTCI values and total accumulative precipitation(TPCP)were very significant for short-time series in comparison to long-time series during 12-yr periods.The weigh correlation coefficients between VTCI and accumulative precipitation decreases with the increase of time series during 2003-2014.This shows that the area witnessed the heavy rainfall and worst flood in the year of 2010 and presents the dry and wet spells with indistinct variation in the precipitation over the region in the 12-yr periods.And disclose that the VTCI values and cumulative precipitation had a significant relationship in different time periods.This demonstrates the VTCI near-real-time drought monitoring approach had the capability with different time scale and time series.This illustrates that the VTCI values had a very significant relationship with the precipitation and demonstrate that the VTCI not only rely on the recent precipitation but it also correlates to elapsed/past precipitation as well as correlates to departure from normal precipitation(DPNP)anomaly.This study reveals the effectiveness of VTCI approach for the determination of warm and cold edges,drought monitoring and flood detection in the given periods over the region.Also,the NRTC approach signifies the relations of VTCI and cumulative precipitation in the validation of dry and wet conditions vigorously.VTCI demonstrate the drought conditions using MODIS NDVI and LST data products in response to drought and soil moisture,which reflects the agricultural and hydrological impact in the plain and shows that VTCI is favorable for the dry and wet condition during the winter wheat crop seasons.This reveals the effectiveness of multi-year MODIS VTCI approach observations for the determination of warm and cold edges,drought monitoring and flood events in the given periods over the plain of Punjab. |
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