Using Observational Precipitation and Evaporation data to investigate the moisture budget in the North Atlantic

Drastic changes occurring in the Arctic in recent years have been a topic of great concern. Changes occurring in the Arctic are largely driven by increases in temperatures, the largest on the Earth, due to global warming and an increase in CO2; a process known as Arctic Amplification. More recently, the Arctic has become warmer and wetter, and evaporation from the ice-free ocean has increased. It is likely that all aspects of the hydrologic cycle are affected by and also feedback on these large and rapid changes occurring in the Arctic. For example, warming temperatures are also associated with a moistening of the atmosphere since warmer air can hold more water vapor, leading to perhaps more intense precipitation and an increase in precipitation in the future. The GPM-IMERG product could be a useful tool to understand changes to precipitation and processes therein in the Arctic where few observations exist. However, here we show that currently it underperforms in the North Atlantic region of the Arctic.

In this work we identify specific synoptic patterns by applying a K-Means clustering procedure to sea level pressure data for the winter season (DJF) between 2003-2018 and focus on the IMERG precipitation anomalies associated with each pattern from the 15-year average. Picking out the most anomalous precipitation cases in the North Atlantic region of the Arctic, we can focus on the physical processes that are related to differences in IMERG and ERA-Interim reanalysis precipitation in these extreme cases. We will also assess the moisture budget (P-E) using observational data (IMERG precipitation and AIRS derived evaporation) as compared to P-E from reanalysis data. We aim to provide an `IMERG-based' precipitation estimate over areas of the Arctic Ocean where IMERG precipitation is currently not produced by attempting to close the moisture budget in the North Atlantic region.