Changes in the Annual Range of Precipitation under Global Warming

Abstract

The annual range of precipitation, which is the difference between maximum and minimum precipitation within a year, is examined in climate model simulations under global warming. For global averages, the annual range of precipitation tends to increase as the globe warms. On a regional basis, this enhancement is found over most areas of the world, except for the bands along 30°S and 30°N. The enhancement in the annual range of precipitation is mainly associated with larger upward trends of maximum precipitation and smaller upward trends or downward trends of minimum precipitation. Based on the moisture budget analysis, the dominant mechanism is vertical moisture advection, both on a global average and on a regional scale. The vertical moisture advection, moisture convergence induced by vertical motion, includes the thermodynamic component, which is associated with increased water vapor, and the dynamic component, which is associated with changes in circulation. Generally, the thermodynamic component enhances the annual range of precipitation, while the dynamic component tends to reduce it. Evaporation has a positive contribution to both maximum and minimum precipitation, but very little to the annual range of precipitation. Even though evaporation and horizontal moisture advection are small for a global average, they could be important on a regional basis.

Future change of the global monsoon revealed from 19 CMIP5 models

“…This implies that the enhanced monsoon variability is a robust signal projected by these coupled models with different model physics, resolutions, and SST warming patterns . The expansion of the GMA is associated with the changes in the annual rainfall cycle in response to greenhouse gas warming forcing [Chou and Lan, 2012]. The CMIP5 models project a wetter summer, but little change to winter rainfall, over global monsoon regions, suggesting that global warming tends to induce an increase in the annual range of monsoon precipitation.…”

“…Very small areas with a decreased GMA are projected. The dominant feature of an expanding GMA may arise from the enhancement of seasonal rainfall cycles under global warming [Chou and Lan, 2012]. Figures 4b and 4c illustrate the monthly rainfall variations within the GMA in the Northern and Southern Hemispheres, respectively.…”

Drivers and mechanisms for enhanced summer monsoon precipitation over East Asia during the mid-Pliocene in the IPSL-CM5A

“…Moisture budget analysis is widely used to understand the global and regional precipitation changes (Yoon and Chen 2005;Chou and Lan 2012;Hsu et al 2012). Here, to estimate the processes that are important for the EASM precipitation, the moisture budget equation is analyzed (Seo et al 2013).…”

“…(1), moisture flux convergence (〈∇ · q � V〉), is further divided into three terms: vertical moisture advection −�ω∂ P q� (ω is vertical velocity Changes of vertical moisture advection can be further divided into thermodynamic and dynamic components, to assess the relative contribution of specific humidity and atmospheric circulation to regional precipitation variability (Chou and Lan 2012). Thus, where − is climatology and 〈 〉′ is the departure of change from the climatology, and − ω∂ p q ′ and − ω ′ ∂ pq denote the thermodynamic and dynamic contribution to the changes of vertical moisture advection, respectively.…”

Projected changes in US rainfall erosivity

“…The strengthening of the robust pattern of anomalies in F compared to annual rainfall is an indication that the seasonal cycle of rainfall will be getting more peaked, i.e., more rain in the rainy season (Chou and Lan, 2012). As noted above, this behavior is more pronounced in the downscaled anomalies, while the same models at the native resolution would indicate negative anomalies extending over Texas, Louisiana, and Mexico (Fig.…”