TY  - JOUR
A1  - Hohenegger, Cathy
A1  - Stevens, Bjorn
T1  - Tropical Continents Rainier Than Expected From Geometrical Constraints
Y1  - 2022-07-06
VL  - 3
IS  - 4
JF  - AGU Advances
DO  - 10.1029/2021AV000636
PB  - 
N2  - Abundant rainfall over tropical land masses sustains rich ecosystems, a crucial source of biodiversity and sink of carbon. Here, we use two characteristics of the observed tropical precipitation distribution, its distinctive zonal arrangement and its partitioning between land and ocean, to understand whether land conditions the climate to receive more than its fair share of precipitation as set by the land‐sea distribution. Our analysis demonstrates that it is not possible to explain the tropics‐wide partitioning of precipitation unless one assumes that rain is favored over land. Land receives more than its fair share of precipitation by broadening and letting the tropical rainbelts move more, effectively underpinning a negative feedback between surface water storage and precipitation. In contrast, rain is disfavored over land in climate models. Our findings suggest that the abundance of rainfall that shapes the terrestrial tropical biosphere is more robust to perturbations than models have suggested.
N2  - Plain Language Summary: Many ecosystems depend on the presence of a land surface exposed to precipitation to exist and prosper. In contrast to the marine biota, though, the terrestrial biosphere cannot directly tap into an unlimited reservoir of water molecules that can be recycled to support life. Yet, observations indicate that it rains in mean 3 mm day−1 over tropical land and 3 mm day−1 over tropical ocean, giving the surprising impression that precipitation amounts are not altered by the presence of land. Investigating the factors controlling this tropics‐wide partitioning of precipitation, we show that geometrical constraints actually would lead to a precipitation ratio of 0.86, not 1.0, if the presence of land would not matter. Comparing this theoretical value to observations, we find that the land receives more than its fair share of precipitation. This happens by broadening and letting the tropical rainbelt moves more over land. By quantifying the strength of the land control on the tropics‐wide partitioning of precipitation, we can also deduce that a negative feedback exists between evapotranspiration and precipitation. In contrast, repeating the same analysis with climate models reveals a positive feedback, questioning the ability of climate models to simulate regional tropical precipitation changes.
N2  - Key Points: A conceptual model of tropical precipitation is derived to understand the tropics‐wide partitioning of precipitation between land and ocean. The size and location of continent constrain the tropical land‐to‐ocean precipitation ratio to lie between 0.74 and 0.95 with a mean of 0.86. Observed ratios from six data sets are larger than these values, indicating that land receives more than its fair share of precipitation.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10252
ER  -