Characterization of Extreme Wet‐Bulb Temperature Events in Southern Pakistan. Issue 17 (9th September 2019)

• Record Type: Journal Article
• Authors: Monteiro, Joy Merwin; Caballero, Rodrigo
• Is Part Of: Geophysical research letters. Volume 46:Issue 17/18(2019)
• Page Start: 10659
• Page End: 10668
• Publication Date: 2019-09-09
• Subjects: extreme events -- heat stress -- Pakistan -- wet bulb temperature -- public health; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL084711
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We study extreme wet‐bulb temperature ( T w ) events in a regional hot spot of high T w values in southwest Pakistan's Indus Valley. We focus on the May–June premonsoon months and employ a combination of station data, ERA‐Interim reanalysis, and trajectory calculations to analyze the extreme events. We find that the events are associated with anomalous influx of marine air from the Arabian Sea. The air flows in a shallow layer below 950 hPa and is heated and moistened by diabatic processes over land, arriving at the hot spot region with very high T w . We surmise that surface evaporation within the strip of well‐irrigated land flanking the Indus River plays a major role in generating these extreme T w values. Our results imply that studies of extreme T w events in future, warmer climates must pay close attention to fine‐scale diabatic processes within the boundary layer, especially evaporation over land. Key Points: Extreme wet‐bulb temperature events in May and June in southern Pakistan identified Extreme events associated with a southerly flow which advects moist oceanic airmass to the region of interest Heating and moistening of the oceanic airmass over land crucial for generating extreme wet‐bulb temperatures