The heat and moisture budget residuals of atmospheric rivers: A multiscale case study

Atmospheric rivers (ARs) are long and narrow regions with high water vapor content in the atmosphere. They play crucial roles in transporting and redistributing heat and moisture in the atmosphere. To understand how convective systems embedded in ARs may heat and dry the ARs, thus affecting the heat and moisture transporting process, two AR events in January 2009 are selected; the thermodynamic impacts (e.g., \u3c Q 1 \u3e,\u3c Q2 \u3e, and heating peaks) of convective systems are quantified; the heating processes (latent heating, radiative forcing, etc.) associated with convective systems are examined; and the ECMWF YOTC data, precipitation observations and cloud observations are investigated. Our main results are: i) convective systems embedded in AR ridges serve as major heat sources (\u3c Q1 \u3e ~ 400–600 W/m2) and moisture sinks (\u3c Q2 \u3e ~ 500–700 W/m2) of ARs; ii) the primary heating peak is between 500–600 hPa when heating is strong; and iii) the primary heating value is on the order of 101 K/day, and can be up to 30 K/day. We hypothesize that convective systems embedded in ARs can not only modulate the amount of moisture transported by ARs, but also modify the moisture origins because i) convective systems can remove moisture from the ARs; therefore, in presence of vigorous convective systems, a large amount of moisture transported from distant regions can be removed; ii) evaporation in presence of mature convective systems can moisten the ARs, this may lead to more localized moisture sources