Abstract. This study examines the diurnal variation in precipitation
over Hainan Island in the South China Sea using
gauge observations from 1951 to 2012 and Climate Prediction
Center MORPHing technique (CMORPH) satellite estimates
from 2006 to 2015, as well as numerical simulations.
The simulations are the first to use climatological mean initial
and lateral boundary conditions to study the dynamic
and thermodynamic processes (and the impacts of land–sea
breeze circulations) that control the rainfall distribution and
climatology. Precipitation is most significant from April to
October and exhibits a strong diurnal cycle resulting from
land–sea breeze circulations. More than 60% of the total annual
precipitation over the island is attributable to the diurnal
cycle with a significant monthly variability. The CMORPH
and gauge datasets agree well, except that the CMORPH
data underestimate precipitation and have a 1 h peak delay.
The diurnal cycle of the rainfall and the related land–
sea breeze circulations during May and June were well captured
by convection-permitting numerical simulations with
the Weather Research and Forecasting (WRF) model, which
were initiated from a 10-year average ERA-Interim reanalysis.
The simulations have a slight overestimation of rainfall
amounts and a 1 h delay in peak rainfall time. The diurnal
cycle of precipitation is driven by the occurrence of moist
convection around noontime owing to low-level convergence
associated with the sea-breeze circulations. The precipitation
intensifies rapidly thereafter and peaks in the afternoon with
the collisions of sea-breeze fronts from different sides of the
island. Cold pools of the convective storms contribute to the
inland propagation of the sea breeze. Generally, precipitation
dissipates quickly in the evening due to the cooling and stabilization
of the lower troposphere and decrease of boundary
layer moisture. Interestingly, the rather high island orography
is not a dominant factor in the diurnal variation in precipitation
over the island.
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Decomposing the Precipitation Response to Climate Change in Convection Allowing Simulations Over the Conterminous United States
Explicit representation of finer‐scale processes can affect the sign and magnitude of the precipitation response to climate change between convection‐permitting and convection‐parameterizing models. We compare precipitation across two 15‐year epochs, a historical (HIST) and an end‐of‐21st‐century (EoC85), between a set of dynamically downscaled regional climate simulations at 3.75 km grid spacing (WRF) and bias‐corrected Community Earth System Model (CESM) output used to initialize and force the lateral boundaries of the downscaled simulations. In the historical climate, the downscaled simulations demonstrate less overall error than CESM when compared to observations for most portions of the conterminous United States. Both sets of simulations overestimate the incidence of environments with moderate to high precipitable water while CESM generally simulates rainfall that is too frequent but less intense. Within both sets of simulations, EoC85 rainfall amounts decrease in low‐moisture environments due to reduced rainfall frequency and intensity while rainfall amounts increase in high‐moisture environments as they occur more often. Overall, reductions in rainfall are stronger in WRF than in CESM, particularly during the warm season. This reduced drying in CESM is attributed to relatively higher rainfall frequency in environments with high concentrations of precipitable water and weak vertical motion. As a result, an increase in the occurrence of high moisture environments in EoC85 naturally favors more rainfall in CESM than WRF. Our results present an in‐depth examination of the characteristics of changes in overall accumulated precipitation and highlight an extra dimension of uncertainty when comparing convection‐permitting models against convection‐parameterizing models.
more » « less- Award ID(s):
- 1637225
- NSF-PAR ID:
- 10478222
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Earth and Space Science
- Volume:
- 10
- Issue:
- 12
- ISSN:
- 2333-5084
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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