Asymmetrical Shift Toward Longer Dry Spells Associated with Warming Temperatures During Russian Summers

This study examines the changing behavior of summer dry spell duration in response to increasing air temperatures at 517 Russian stations during 1966-2010. We found that the frequency distribution of dry spell duration (as represented by histograms) is becoming skewed toward longer dry spells. This asymmetrical shift is accompanied by mean increases in dry spell duration. This asymmetry is also reflected in exponentially higher increasing rates of dry spell duration toward higher percentiles. Consequently, across Russia, summers have experienced significant increases in 7-day-or-longer dry spells (at 6.1%/°C of warming) and fewer occurrences of 3-day-or-shorter dry spells (at 2.4%/°C). This study suggests that hotter summers favor more frequent prolonged dry spells, exacerbating drought and heat wave conditions during Russian summers as air temperatures continue to rise.