TY - JOUR
T1 - Gravity Waves and Other Mechanisms Modulating the Diurnal Precipitation over One of the Rainiest Spots on Earth
T2 - Observations and Simulations in 2016
AU - Yepes, Johanna
AU - Mejía, John F.
AU - Mapes, Brian
AU - Poveda, Germán
N1 - Funding Information:
Acknowledgments. We are grateful with scientists, students, collaborators, and local volunteers from Universidad Nacional de Colombia at Medellín, Universidad Tecnológica del Chocó at Quibdó, DIMAR, FAC, DRI who participated in the planning, execution, and data gathering during ChocoJEX. We also thank Wei-Ming Tsai for helping us with the MSE plots through his open access Python package called MSE-plots. The work of Johanna Yepes was funded by COLCIENCIAS Doctorate Fellowship Program. COLCIENCIAS and the DRI and its Division of Atmospheric Sciences (DAS) partially supported J. F. Mejia. The work of G. Poveda is funded by Universidad Nacional de Colombia at Medellín, Colombia. The work of B. Mapes was supported by NASA NEWS program Grant NNX15AD11G and by the National Science Foundation under Grant 1639722.
Publisher Copyright:
© 2020 American Meteorological Society. All rights reserved.
PY - 2020/9
Y1 - 2020/9
N2 - The diurnal cycle of precipitation and thermodynamic profiles over western Colombia are examined in new GPM satellite rainfall products, first-ever research balloon launches during 2016 over both sea and land, and numerical simulations with the Weather Research and Forecasting (WRF) Model. This paper evaluates the Mapes et al. mechanism for midnight–early morning coastal convection that propagates offshore: reduction of inhibition in the crests of lower-tropospheric internal waves. Shipborne balloon launches confirm the evening development of such inhibition by a warm overhang in saturation moist static energy (SMSE) near 700–800 hPa. This feature relaxes overnight, consistent with the disinhibition hypothesis for early morning rains. Over the coastal plain, soundings also show late afternoon increases in near-surface MSE large enough to predominate over the overhang’s inhibition effect, driving a second peak in the rainfall diurnal cycle. Parameterized convection simulations fail to simulate the observed coastal rainfall. Still, during a November 2016 wet spell, a cloud-permitting one-way nested 4 km simulation performs better, simulating morning coastal rainfall. In that simulation, however, early morning cooling in the 700–800 hPa layer appears mainly as a standing signal resembling the local radiative effect rather than as a propagating wave. We consider the additional hypothesis that the offshore propagation of that morning convection could involve advection or wind shear effects on organized convective systems. Strong easterlies at mountaintop level were indeed simulated, but that is one of the model’s strongest biases, so the mechanisms of the model’s partial success in simulating diurnal rainfall remain ambiguous.
AB - The diurnal cycle of precipitation and thermodynamic profiles over western Colombia are examined in new GPM satellite rainfall products, first-ever research balloon launches during 2016 over both sea and land, and numerical simulations with the Weather Research and Forecasting (WRF) Model. This paper evaluates the Mapes et al. mechanism for midnight–early morning coastal convection that propagates offshore: reduction of inhibition in the crests of lower-tropospheric internal waves. Shipborne balloon launches confirm the evening development of such inhibition by a warm overhang in saturation moist static energy (SMSE) near 700–800 hPa. This feature relaxes overnight, consistent with the disinhibition hypothesis for early morning rains. Over the coastal plain, soundings also show late afternoon increases in near-surface MSE large enough to predominate over the overhang’s inhibition effect, driving a second peak in the rainfall diurnal cycle. Parameterized convection simulations fail to simulate the observed coastal rainfall. Still, during a November 2016 wet spell, a cloud-permitting one-way nested 4 km simulation performs better, simulating morning coastal rainfall. In that simulation, however, early morning cooling in the 700–800 hPa layer appears mainly as a standing signal resembling the local radiative effect rather than as a propagating wave. We consider the additional hypothesis that the offshore propagation of that morning convection could involve advection or wind shear effects on organized convective systems. Strong easterlies at mountaintop level were indeed simulated, but that is one of the model’s strongest biases, so the mechanisms of the model’s partial success in simulating diurnal rainfall remain ambiguous.
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U2 - 10.1175/MWR-D-19-0405.1
DO - 10.1175/MWR-D-19-0405.1
M3 - Article
AN - SCOPUS:85098974380
VL - 148
SP - 3933
EP - 3950
JO - Monthly Weather Review
JF - Monthly Weather Review
SN - 0027-0644
IS - 9
ER -