scholarly journals Diurnal Cycle of Summer Precipitation over Subtropical East Asia in CAM5

2013 ◽  
Vol 26 (10) ◽  
pp. 3159-3172 ◽  
Author(s):  
Weihua Yuan ◽  
Rucong Yu ◽  
Minghua Zhang ◽  
Wuyin Lin ◽  
Jian Li ◽  
...  
Keyword(s):  
East Asia ◽  
Diurnal Cycle ◽  
Large Scale ◽  
Early Morning ◽  
Convective Precipitation ◽  
Total Rainfall ◽  
Low Level ◽  
Resolution Model ◽  
Diurnal Rainfall ◽  
Stratiform Rainfall

Abstract The simulations of summertime diurnal cycle of precipitation and low-level winds by the Community Atmosphere Model, version 5, are evaluated over subtropical East Asia. The evaluation reveals the physical cause of the observed diurnal rainfall variation in East Asia and points to the source of model strengths and weaknesses. Two model versions with horizontal resolutions of 2.8° and 0.5° are used. The models can reproduce the diurnal phase of large-scale winds over East Asia, with an enhanced low-level southwesterly in early morning. Correspondingly, models successfully simulated the diurnal variation of stratiform rainfall with a maximum in early morning. However, the simulated convective rainfall occurs at local noontime, earlier than observations and with larger amplitude (normalized by the daily mean). As a result, models simulated a weaker diurnal cycle in total rainfall over the western plain of China due to an out-of-phase cancellation between convective and stratiform rainfalls and a noontime maximum of total rainfall over the eastern plain of China. Over the East China Sea, models simulated the early-morning maximum of convective precipitation and, together with the correct phase of the stratiform rainfall, they captured the diurnal cycle of total precipitation. The superposition of the stratiform and convective rainfalls also explains the observed diurnal cycle in total rainfall in East Asia. Relative to the coarse-resolution model, the high-resolution model simulated slight improvement in diurnal rainfall amplitudes, due to the larger amplitude of stratiform rainfall. The two models, however, suffer from the same major biases in rainfall diurnal cycles due to the convection parameterization.

Intraseasonal Variability in Diurnal Rainfall over New Guinea and the Surrounding Oceans during Austral Summer

2008 ◽  
Vol 21 (12) ◽  
pp. 2852-2868 ◽  
Author(s):  
Hiroki Ichikawa ◽  
Tetsuzo Yasunari
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Intraseasonal Variability ◽  
Phase Speed ◽  
New Guinea ◽  
Space Structure ◽  
Local Circulation ◽  
Large Scale Circulation ◽  
Low Level ◽  
Diurnal Rainfall

Abstract High-resolution Tropical Rainfall Measuring Mission (TRMM) rainfall data for six wet seasons (December–March) were used to investigate the time and space structure of the diurnal cycle of rainfall over and around New Guinea, a major island of the Maritime Continent. The diurnal cycle shows a systematic modulation associated with intraseasonal variability in the large-scale circulation pattern, with regimes associated with low-level easterlies or westerlies over the island. Lower-tropospheric easterly (westerly) wind components correspond to periods of inactive (active) convection over the islands that are associated with the passage of intraseasonal atmospheric disturbances such as the Madden–Julian oscillation (MJO). A striking feature is the diurnal rainfall that develops over the central mountain ranges in the evening and propagates toward the southwest (northeast) of the island with an inferred phase speed of about 2–3 m s−1 under low-level easterly (westerly) flow. In the case of the easterly regime, diurnal rainfall is strongly concentrated over the southwestern part of the island, inhibited from spreading offshore southwest of New Guinea. Under the westerly regime, in contrast, the rainfall area spread far and wide along the low-level westerlies from the island toward the Pacific Ocean. Significant offshore rainfall propagation extending from the island appears during the night over the north-northeastern coast and moves with a phase speed of about 7–8 m s−1, reaching the open ocean the following day. Possible processes for controlling the variability in diurnal rainfall through the interaction between large-scale circulation and previously denoted complex local circulation over the island are discussed.

scholarly journals Detecting and Tracking Coastal Precipitation in the Tropics: Methods and Insights into Multiscale Variability of Tropical Precipitation

2020 ◽  
Vol 33 (15) ◽  
pp. 6689-6705
Author(s):  
David Coppin ◽  
Gilles Bellon ◽  
Alexander Pletzer ◽  
Chris Scott
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Total Rainfall ◽  
Tropical Precipitation ◽  
Precipitation Estimates ◽  
Summer Hemisphere ◽  
The Tropics ◽  
Climate Prediction Center

AbstractWe propose an algorithm to detect and track coastal precipitation systems and we apply it to 18 years of the high-resolution (8 km and 30 min) Climate Prediction Center CMORPH precipitation estimates in the tropics. Coastal precipitation in the Maritime Continent and Central America contributes to up to 80% of the total rainfall. It also contributes strongly to the diurnal cycle over land with the largest contribution from systems lasting between 6 and 12 h and contributions from longer-lived systems peaking later in the day. While the diurnal cycle of coastal precipitation is more intense over land in the summer hemisphere, its timing is independent of seasons over both land and ocean because the relative contributions from systems of different lifespans are insensitive to the seasonal cycle. We investigate the hypothesis that coastal precipitation is enhanced prior to the arrival of the Madden–Julian oscillation (MJO) envelope over the Maritime Continent. Our results support this hypothesis and show that, when considering only coastal precipitation, the diurnal cycle appears reinforced even earlier over islands than previously reported. We discuss the respective roles of coastal and large-scale precipitation in the propagation of the MJO over the Maritime Continent. We also document a shift in diurnal cycle with the phases of the MJO, which results from changes in the relative contributions of short-lived versus long-lived coastal systems.

Parameter Tuning and Calibration of RegCM3 with MIT–Emanuel Cumulus Parameterization Scheme over CORDEX East Asia Domain

2014 ◽  
Vol 27 (20) ◽  
pp. 7687-7701 ◽  
Author(s):  
Liwei Zou ◽  
Yun Qian ◽  
Tianjun Zhou ◽  
Ben Yang
Keyword(s):  
East Asia ◽  
Regional Climate ◽  
Cumulus Parameterization ◽  
Parameterization Scheme ◽  
Cumulus Parameterization Scheme ◽  
Convection Scheme ◽  
Total Rainfall ◽  
Low Level ◽  
Positive Effects ◽  
Cordex East Asia

Abstract In this study, the authors calibrated the performance of the Regional Climate Model, version 3 (RegCM3), with the Massachusetts Institute of Technology (MIT)–Emanuel cumulus parameterization scheme over the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia domain by tuning seven selected parameters based on the multiple very fast simulated annealing (MVFSA) approach. The seven parameters were selected based on previous studies using RegCM3 with the MIT–Emanuel convection scheme. The results show the simulated spatial pattern of rainfall, and the probability density function distribution of daily rainfall rates is significantly improved in the optimal simulation. Sensitivity analysis suggests that the parameter relative humidity criteria (RHC) has the largest effect on the model results. Followed by an increase of RHC, an increase of total rainfall is found over the northern equatorial western Pacific, mainly contributed by the increase of explicit rainfall. The increases of the convergence of low-level water vapor transport and the associated increases in cloud water favor the increase of explicit rainfall. The identified optimal parameters constrained by total rainfall have positive effects on the low-level circulation and surface air temperature. Furthermore, the optimized parameters based on the chosen extreme case are transferable to a normal case and the model’s new version with a mixed convection scheme.

Gravity Waves and Other Mechanisms Modulating the Diurnal Precipitation over One of the Rainiest Spots on Earth: Observations and Simulations in 2016

2020 ◽  
Vol 148 (9) ◽  
pp. 3933-3950
Author(s):  
Johanna Yepes ◽  
John F. Mejía ◽  
Brian Mapes ◽  
Germán Poveda
Keyword(s):  
Diurnal Cycle ◽  
Wrf Model ◽  
Early Morning ◽  
Weather Research And Forecasting ◽  
Near Surface ◽  
Additional Hypothesis ◽  
Convective Systems ◽  
Earth Observations ◽  
Diurnal Rainfall ◽  
Static Energy

ABSTRACT 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.

The Diurnal Cycle of Rainfall and the Convectively Coupled Equatorial Waves over the Maritime Continent

2020 ◽  
Vol 33 (8) ◽  
pp. 3307-3331 ◽  
Author(s):  
Naoko Sakaeda ◽  
George Kiladis ◽  
Juliana Dias
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Vertical Motion ◽  
Equatorial Waves ◽  
Maritime Continent ◽  
Moisture Profile ◽  
Convectively Coupled Equatorial Waves ◽  
Large Scale Disturbance ◽  
Diurnal Rainfall ◽  
Equatorial Rossby Waves

AbstractPrecipitation variability over the Maritime Continent is predominantly explained by its diurnal cycle and large-scale disturbances such as the Madden–Julian oscillation (MJO) and convectively coupled equatorial waves (CCEWs). To advance our understanding of their interactions and physical processes, this study uses satellite data to examine changes in the diurnal cycle of rainfall associated with the MJO and CCEWs over the Maritime Continent. We find that diurnal cycle modulations associated with the passage of any type of large-scale disturbance are closely tied to changes in rain types and land–sea diurnal propagation of rainfall. When the amplitude of the diurnal cycle increases over the islands, the phase of the diurnal cycle is delayed by a few hours as clouds are more organized and rainfall from stratiform-anvil clouds increases. Enhanced amplitude of the diurnal cycle can alter the speed of land–sea diurnal propagation of rainfall, which then influences the timing of diurnal rainfall over coastal regions. These changes in the diurnal cycle occur asymmetrically across the island terrain associated with the MJO and equatorial Rossby waves, while such asymmetric modulations are not observed for other waves. Geographical and wave dependencies of the diurnal cycle are linked to differences in large-scale lower tropospheric wind, vertical motion, and moisture profile perturbations, which are in turn tied to differences in cloud population evolution. The results of this study highlight the importance of further improving our understanding of the sensitivity of cloud populations to varying large-scale phenomena.

scholarly journals Mechanism of Orographic Precipitation around the Meghalaya Plateau Associated with Intraseasonal Oscillation and the Diurnal Cycle

2013 ◽  
Vol 141 (7) ◽  
pp. 2451-2466 ◽  
Author(s):  
Tomonori Sato
Keyword(s):  
Diurnal Cycle ◽  
Intraseasonal Oscillation ◽  
Lower Troposphere ◽  
Atmospheric Model ◽  
Early Morning ◽  
Northeast India ◽  
Orographic Precipitation ◽  
Active Period ◽  
Low Level ◽  
Inactive Period

Abstract Mesoscale processes that cause tremendous amounts of precipitation around the Meghalaya Plateau, northeast India, were investigated using a regional atmospheric model, with a particular focus on the possible role of an intraseasonal oscillation (ISO) and the diurnal cycle. A numerical experiment was conducted using the Weather Research and Forecasting Model (WRF) to simulate a prominent submonthly-scale ISO event observed during June–July 2004. A WRF experiment successfully simulated the timing and magnitude of precipitation during the first active period and subsequent inactive period of the ISO, despite large biases in the second active period. The WRF experiment revealed that the magnitude of prevailing southwesterly winds in the lower troposphere differs significantly between active and inactive periods; strong southwesterly flow transports abundant moisture to the southern slope of the Meghalaya Plateau during the active period, which triggers forced lifting and brings orographic precipitation. However, low-level wind during the inactive period is too weak to overcome the vertical stratification barrier; hence, it is unable to reach the condensation level. The WRF experiment suggested that the diurnal cycle of precipitation is enhanced during the active period, exhibiting an evening to early morning maximum, as observed by the Tropical Rainfall Measuring Mission (TRMM). The experiment also indicated a prominent nocturnal low-level jet (LLJ) appearing at 900 hPa. The direction of the LLJ varies clockwise with time, which accelerates the preexisting southwesterly flow during 1800–0600 LT. The diurnal variation of the LLJ is responsible for the evening to early morning maximum of precipitation, thus contributing to the precipitation variability in the ISO.

scholarly journals Robust Nocturnal and Early Morning Summer Rainfall Peaks over Continental East Asia in a Global Multiscale Modeling Framework

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 53 ◽  
Author(s):  
Yi Zhang ◽  
Haoming Chen ◽  
Dan Wang
Keyword(s):  
East Asia ◽  
Multiscale Modeling ◽  
Diurnal Cycle ◽  
Summer Rainfall ◽  
Early Morning ◽  
Atmospheric Modeling ◽  
The Tibetan Plateau ◽  
Moderate Increase ◽  
Modeling Framework ◽  
Multiscale Modeling Framework

The diurnal cycle of convection and precipitation is an important atmospheric feature. It also poses a great challenge to global numerical atmospheric modeling. Over continental East Asia, most global models cannot well capture the nocturnal and early morning peaks of summer rainfall. This problem may lead to dry biases and limit the modeling skills. This study investigates this problem using a global multiscale modeling framework (Super-Parameterized CAM5; SPCAM5). The nocturnal and early morning peaks, which are almost absent in CAM5 and a coarser-resolution SPCAM5, can be successfully captured by SPCAM5 with a moderate increase in the horizontal resolution. On the lee side of the Tibetan Plateau, SPCAM5 generates robust eastward propagating rainfall signals, which correspond to the moving convective systems, as revealed by the heating and drying profiles. Over the eastern plain of China, the early morning peaks become more evident, corresponding to a stratiform-type heating structure in the midlevel. A sensitivity experiment with altered grid-scale forcing also suggests the important preconditioning role of the vertical moisture advection in regulating the early morning peaks. These results highlight the added value of representing multiscale processes to the successful simulation of the diurnal cycle over continental East Asia.

scholarly journals Role of the Kuroshio Current on the Diurnal Variation of the Early-Summer Meiyu-Baiu Rainband

2021 ◽  
Author(s):  
Hyung-Ju Park ◽  
Kwang-Yul Kim
Keyword(s):  
Diurnal Cycle ◽  
Convective Instability ◽  
Large Scale ◽  
Surface Wind ◽  
Kuroshio Current ◽  
Early Summer ◽  
Convective Precipitation ◽  
Diurnal Cycle Of Precipitation ◽  
The Kuroshio ◽  
Baiu Front

Abstract Mechanism of the strong diurnal cycle of precipitation over the Kuroshio Current (KC) during mid-June is investigated, when the climatological location of the Meiyu-Baiu front overlaps the KC. Heating from the KC intensifies in the morning when the temperature difference between the sea surface and the surface air (TDF) maximizes. The diurnal cycle of precipitation, on the other hand, peaks in the afternoon, consistent with previous studies. It is revealed that convective precipitation (CP) due to convective instability is in phase with TDF, whereas large-scale precipitation (LSP) caused by the cross-frontal circulation matures later. Intensified convective instability via enhanced heating from the KC in the morning hours (03–12 LST) increases the mean amount of CP as well as the probability of stronger CP. Surface wind convergence is also strengthened during the morning hours and helps sustain the convection. The diurnal cycle of LSP, which peaks in the afternoon hours (12–15 LST), covaries with the intensity of the Meiyu-Baiu front and the assocaited cross-frontal circulation. The wind convergence and deformation anomalies associated with the intensified thermal heating over the KC during the morning hours intensifies the frontogenesis function, which leads to the maximization of the frontal intensity in the afternoon. The direct contribution of diabatic heating to the frontogenesis is relatively weak.

Entangled impacts of large-scale monsoon flows and terrain circulations on the diurnal cycle of rainfall over the Himalayas

2021 ◽  
Keyword(s):  
High Altitude ◽  
Diurnal Cycle ◽  
Bay Of Bengal ◽  
Large Scale ◽  
Early Morning ◽  
Atmospheric Layer ◽  
Rainfall Total ◽  
Monsoon Flow ◽  
Downslope Flow

Abstract The diurnal features of rainfall over the Himalayas have been widely investigated, but their triggers remain unclear. In this work, we divided the Himalayas and surroundings into four regions, including the plains, foothills, slopes, and plateau, and investigated the above issues. The results show that the rainfall total is controlled by large-scale monsoon flows while its meridional distribution is regulated by terrain circulations. The afternoon rainfall peak in the plains and foothills is linked with the intersection of two monsoon flows. The southward-shifting rainfall peak, which occurs from midnight to early morning in the slopes and foothills, is affected by the nighttime downslope flow and the strong Bay of Bengal monsoon flow in the morning. The evening rainfall peak in the plateau and high-altitude slopes is thought to be a result of the atmospheric layer being at its moistest at that time.

Formation of Nocturnal Offshore Rainfall near the West Coast of Sumatra: Land Breeze or Gravity Wave?

2021 ◽  
Vol 149 (3) ◽  
pp. 715-731
Author(s):  
Hedanqiu Bai ◽  
Gumilang Deranadyan ◽  
Courtney Schumacher ◽  
Aaron Funk ◽  
Craig Epifanio ◽  
...  
Keyword(s):  
West Coast ◽  
Large Scale ◽  
Deep Convection ◽  
Propagation Speed ◽  
Early Morning ◽  
Land Breeze ◽  
Maritime Continent ◽  
The West ◽  
Rainfall Events ◽  
Low Level

AbstractAfternoon deep convection over the Maritime Continent islands propagates offshore in the evening to early morning hours, leading to a nocturnal rainfall maximum over the nearby ocean. This work investigates the formation of the seaward precipitation migration off western Sumatra and its intraseasonal and seasonal characteristics using BMKG C-band radar observations from Padang and ERA5 reanalysis. A total of 117 nocturnal offshore rainfall events were identified in 2018, with an average propagation speed of 4.5 m s−1 within 180 km of Sumatra. Most offshore propagation events occur when the Madden–Julian oscillation (MJO) is either weak (real-time multivariate MJO index < 1) or active over the Indian Ocean (phases 1–3), whereas very few occur when the MJO is active over the Maritime Continent and western Pacific Ocean (phases 4–6). The occurrence of offshore rainfall events also varies on the basis of the seasonal evolution of the large-scale circulation associated with the Asian–Australian monsoons, with fewer events during the monsoon seasons of December–February and June–August and more during the transition seasons of March–May and September–November. Low-level convergence, resulting from the interaction of the land breeze and background low-level westerlies, is found to be the primary driver for producing offshore convective rain propagation from the west coast of Sumatra. Stratiform rain propagation speeds are further increased by upper-level easterlies, which explains the faster migration speed of high reflective clouds observed by satellite. However, temperature anomalies associated with daytime convective latent heating over Sumatra indicate that gravity waves may also modulate the offshore environment to be conducive to seaward convection migration.

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