Global Scaling of Rainfall With Dewpoint Temperature Reveals Considerable Ocean‐Land Difference

다국어 초록 (Multilingual Abstract)

Short‐duration rainfall extremes are expected to intensify with warming at around 7%/K, following the Clausius‐Clapeyron (CC) relation, causing concomitant increases in flash floods. Observed hourly rainfall extremes show consistent CC‐scaling with dewpoint temperature across all land regions. Here, we use two global climate reanalysis products (ERA5 and MERRA‐2) to examine consistency in scaling with observations, in ungauged regions and over the oceans. We find that reanalyzes underestimate observed scaling, but ERA5 provides better estimates than MERRA‐2. Scaling rates at high latitudes and midlatitudes are similar to observations, at CC, while over the tropics mixed negative‐ and super‐CC scaling rates are seen. We show underestimation of scaling rates over the tropics is related to deficiencies in simulations of extreme rainfall over orographically complex and convection dominated regions. Importantly, both reanalyzes indicate scaling rates over the ocean are substantially higher than over land, with implications for extreme weather events originating over the ocean.
As temperatures rise, extreme rainfalls are expected to intensify by 7% per 1°C following the Clausius‐Clapeyron relation. Thus, flash floods are predicted to increase in magnitude and frequency with rising temperatures. In the areas where measurements are available, observations confirm the intensification of extreme hourly rainfall with increasing temperatures at the expected rate. Here, we use two global climate reanalysis products to examine the agreement in extreme rainfall‐temperature relation with observations, in ungauged regions and over the ocean. High‐latitude and midlatitude rainfall‐temperature rates obtained from the climate reanalysis are in accordance with observations. In the tropics, the rainfall‐temperature relation is a mix of negative and very high values (in the order of 14% per 1°C). Climate reanalyzes indicate extreme rainfall‐temperature rates are much higher over the ocean than on land.



Hourly precipitation‐temperature scaling was computed using MERRA‐2 and ERA‐5 at a global scale

Scaling patterns in ERA‐5 are closer to those obtained from the Global Subdaily Rainfall (GSDR) data set

Scaling rates over ocean were found to be substantially higher than over land


Hourly precipitation‐temperature scaling was computed using MERRA‐2 and ERA‐5 at a global scale
Scaling patterns in ERA‐5 are closer to those obtained from the Global Subdaily Rainfall (GSDR) data set
Scaling rates over ocean were found to be substantially higher than over land