The influence of sea- and land-breeze circulations on the diurnal variability in precipitation over a tropical island

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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The influence of sea- and land-breeze circulations on the diurnal variability of precipitation over a tropical island

10.5194/acp-2017-332 ◽

2017 ◽

Author(s):

Lei Zhu ◽

Zhiyong Meng ◽

Fuqing Zhang ◽

Paul M. Markowski

Keyword(s):

Diurnal Variation ◽

Numerical Simulations ◽

Diurnal Cycle ◽

Lower Troposphere ◽

Sea Breeze ◽

Hainan Island ◽

Dominant Factor ◽

Land Breeze ◽

Moist Convection ◽

Diurnal Variability

Abstract. This study examines the diurnal variation of precipitation over Hainan Island in the South China Sea using gauge observations from 1950 to 2010 and CMORPH satellite estimates from 2006 to 2015, as well as numerical simulations. 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 as well. The CMORPH and gauge datasets agree well, except that the CMORPH data underestimates precipitation and has a 1-h delay of peaks. The diurnal cycle of the rainfall and the related land/sea breeze circulations during May and June were well captured by convection-allowing numerical simulations with WRF, which were initiated from 10-year average ERA-interim reanalysis, despite slightly overall overestimation and 1-h delay of the rainfall peak. The diurnal precipitation is due to a diurnal cycle of moist convection, which initiates around noontime owing to low-level convergence associated with the sea breeze circulation. 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. The precipitation dissipates quickly in the evening owing 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 of the precipitation over the island.

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Characterizing the diurnal cycle of South Atlantic stratocumulus cloud properties from satellite retrievals

10.5194/acp-2018-445 ◽

2018 ◽

Author(s):

Chellappan Seethala ◽

Jan Fokke Meirink ◽

Ákos Horváth ◽

Ralf Bennartz ◽

Rob Roebeling

Keyword(s):

Diurnal Variation ◽

Biomass Burning ◽

Diurnal Cycle ◽

Near Infrared ◽

South Atlantic ◽

Radiation Budget ◽

Ozone Monitoring Instrument ◽

Liquid Water Path ◽

Diurnal Variability ◽

Late Afternoon

Abstract. Marine stratocumulus (Sc) clouds play an essential role in the earth radiation budget. Here, we compare liquid water path (LWP), optical thickness (COT), and effective radius (CER) retrievals from two years of collocated Spinning Enhanced Visible and InfraRed Imager (SEVIRI), MODerate resolution Imaging Spectroradiometer (MODIS), and Tropical Rainfall Measuring Mission Microwave Imager (TMI) observations, estimate the effect of biomass burning smoke on passive imager retrievals, as well as evaluate the diurnal cycle of South Atlantic marine Sc clouds. The effect of absorbing aerosols from biomass burning on the retrievals was investigated using aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI). SEVIRI and MODIS LWPs were found to decrease with increasing AI relative to TMI LWP, consistent with well-known negative visible/near-infrared retrieval biases in COT and CER. In the aerosol-affected months of July–August–September, SEVIRI LWP – based on the 1.6-µm CER – was biased low by 14 g m−2 (~ 16 %) compared to TMI in overcast scenes, while MODIS LWP showed a smaller low bias of 4 g m−2 (~ 5 %) for the 1.6-µm channel and a high bias of 8 g m−2 (~ 10 %) for the 3.7-µm channel compared to TMI. Neglecting aerosol-affected pixels reduced the mean SEVIRI-TMI LWP bias considerably. On a two-year data base, SEVIRI LWP had a correlation with TMI and MODIS LWP of about 0.86 and 0.94, respectively, and biases of only 4–8 g m−2 (5–10 %) for overcast cases. The SEVIRI LWP diurnal cycle was in good overall agreement with TMI except in the aerosol-affected months. Both TMI and SEVIRI LWP decreased from morning to late afternoon, after which a slight increase was observed. Terra and Aqua MODIS mean LWPs also suggested a similar diurnal variation. The relative amplitude of the two-year mean and seasonal mean LWP diurnal cycle varied between 35–40 % from morning to late afternoon for overcast cases. The diurnal variation in SEVIRI LWP was mainly due to changes in COT, while CER showed only little diurnal variability.

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Numerical Study of the Effects of Topography and Urbanization on the Local Atmospheric Circulations over the Beijing-Tianjin-Hebei, China

Advances in Meteorology ◽

10.1155/2015/397070 ◽

2015 ◽

Vol 2015 ◽

pp. 1-16 ◽

Cited By ~ 20

Author(s):

Yucong Miao ◽

Shuhua Liu ◽

Yijia Zheng ◽

Shu Wang ◽

Bicheng Chen

Keyword(s):

Numerical Study ◽

Wrf Model ◽

Sea Breeze ◽

Land Breeze ◽

Bohai Bay ◽

Breeze Circulation ◽

Thermally Induced ◽

Atmospheric Circulations ◽

Mountain Valley ◽

Bth Region

The effects of the topography and urbanization on the local atmospheric circulations over the Beijing-Tianjin-Hebei (BTH) region were studied by the weather research and forecasting (WRF) model, as well as the interactions among these local atmospheric circulations. It was found that, in the summer day time, the multiscale thermally induced local atmospheric circulations may exist and interact in the same time over the BTH region; the topography played a role in the strengthening of the sea breeze circulations; after sunset, the inland progress of sea breeze was slowed down by the opposite mountain breeze; when the land breeze circulation dominated the Bohai bay, the mountain breeze circulation can couple with the land breeze circulation to form a large circulation ranging from the coastline to the mountains. And the presence of cities cannot change the general state of the sea-land breeze (SLB) circulation and mountain-valley breeze (MVB) circulation but acted to modify these local circulations slightly. Meanwhile, the development of the urban heat island (UHI) circulation was also strongly influenced by the nearby SLB circulation and MVB circulation.

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Observations and Modeling of the Surface Aerosol Radiative Forcing during UAE2

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2555.1 ◽

2008 ◽

Vol 65 (9) ◽

pp. 2877-2891 ◽

Cited By ~ 21

Author(s):

K. M. Markowicz ◽

P. J. Flatau ◽

J. Remiszewska ◽

M. Witek ◽

E. A. Reid ◽

...

Keyword(s):

United Arab Emirates ◽

Radiative Forcing ◽

Sea Breeze ◽

Single Scattering ◽

Land Breeze ◽

Gulf Region ◽

Diurnal Variability ◽

Aerosol Radiative Forcing ◽

Aerosol Forcing ◽

Aerosol Radiative

Abstract Aerosol radiative forcing in the Persian Gulf region is derived from data collected during the United Arab Emirates (UAE) Unified Aerosol Experiment (UAE2). This campaign took place in August and September of 2004. The land–sea-breeze circulation modulates the diurnal variability of the aerosol properties and aerosol radiative forcing at the surface. Larger aerosol radiative forcing is observed during the land breeze in comparison to the sea breeze. The aerosol optical properties change as the onshore wind brings slightly cleaner air. The mean diurnal value of the surface aerosol forcing during the UAE2 campaign is about −20 W m−2, which corresponds to large aerosol optical thickness (0.45 at 500 nm). The aerosol forcing efficiency [i.e., broadband shortwave forcing per unit optical depth at 550 nm, W m−2 (τ500)−1] is −53 W m−2 (τ500)−1 and the average single scattering albedo is 0.93 at 550 nm.

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Recovery processes in coastal wind farms under sea-breeze conditions

Advances in Geosciences ◽

10.5194/adgeo-56-129-2021 ◽

2021 ◽

Vol 56 ◽

pp. 129-139

Author(s):

Tanvi Gupta ◽

Somnath Baidya Roy

Keyword(s):

Wind Farm ◽

Wrf Model ◽

Wind Farms ◽

Sea Breeze ◽

Offshore Wind ◽

Dominant Factor ◽

Offshore Wind Farms ◽

Sea Breezes ◽

Wind Speeds ◽

Recovery Processes

Abstract. With the rapid growth in offshore wind energy, it is important to understand the dynamics of offshore wind farms. Most of the offshore wind farms are currently installed in coastal regions where they are often affected by sea-breezes. In this work, we quantitatively study the recovery processes for coastal wind farms under sea-breeze conditions. We use a modified Borne's method to identify sea breeze days off the west coast of India in the Arabian Sea. For the identified sea breeze days, we simulate a hypothetical wind farm covering 50×50 km2 area using the Weather Research and Forecasting (WRF) model driven by realistic initial and boundary conditions. We use three wind farm layouts with the turbines spaced 0.5, 1, and 2 km apart. The results show an interesting power generation pattern with a peak at the upwind edge and another peak at the downwind edge due to sea breeze. Wind farms affect the circulation patterns, but the effects of these modifications are very weak compared to the sea breezes. Vertical recovery is the dominant factor with more than half of the momentum extracted by wind turbines being replenished by vertical turbulent mixing. However, horizontal recovery can also play a strong role for sparsely packed wind farms. Horizontal recovery is stronger at the edges where the wind speeds are higher whereas vertical recovery is stronger in the interior of the wind farms. This is one of the first studies to examine replenishment processes in offshore wind farms under sea breeze conditions. It can play an important role in advancing our understanding wind farm-atmospheric boundary layer interactions.

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Analyzing the atmospheric scales involved in sea-breeze formation and frontal characteristics

10.5194/egusphere-egu2020-3041 ◽

2020 ◽

Author(s):

Jon Ander Arrillaga ◽

Pedro Jiménez ◽

Jordi Vilà-Guerau de Arellano ◽

Maria Antonia Jiménez ◽

Carlos Román-Cascón ◽

...

Keyword(s):

Numerical Simulations ◽

Large Scale ◽

Surface Wind ◽

Sensible Heat Flux ◽

Wrf Model ◽

Sea Breeze ◽

Stable Stratification ◽

Horizontal Resolution ◽

Sea Temperature ◽

The Moment

We investigate sea-breeze (SB) frontal passages troughout a 10-year period. Spanning the whole period, numerical simulations from the Weather Research and Forecasting (WRF) model are compared with a comprehensive observational database from the Cabauw Experimental Site (Ruisdael Project). On the one hand, a fine horizontal resolution of 2 km is employed in the numerical simulations, and the observational vertical levels within the first 200 m above the surface are replicated. On the other hand, an algorithm based on objective and strict filters is applied to both observations and simulations to select the SB events. This methodology allows to investigate the atmospheric scales influencing the SB formation and their interaction with local turbulence in a robust and objective way.By carrying out a filter-by-filter comparison, we find that the simulated large-scale conditions show a good rate of coincidence with the observations (69%). Small biases in the large scale wind direction, however, induce important deviations in the surface-wind evolution. Regarding the mesoscale forcings, the land-sea temperature gradient is overestimated in average up to 4 K, producing stronger SB fronts in WRF. The analysis of the SB frontal characteristics and impacts is carried out by classifying the events into three boundary-layer regimes (convective, transition and stable) based on the value of the sensible-heat flux at the moment of the SB onset. The stronger SB in the model leads to enhanced turbulence particularly in the convective and transition regimes: the friction velocity, for instance, is overstated by around 50% at the SB onset. In addition, the arrival of the SB front enhances the stable stratification and gives rise to faster afternoon and evening transitions compared with situations solely driven by local atmospheric turbulence.The obtained results can be considered a benchmark of the aspects to be improved in order to produce finer SB forecasts and more adequate representations of the associated physical processes, particularly during the afternoon and evening transition of the ABL.

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The Tokar Gap Jet: Regional Circulation, Diurnal Variability, and Moisture Transport Based on Numerical Simulations

Journal of Climate ◽

10.1175/jcli-d-14-00635.1 ◽

2015 ◽

Vol 28 (15) ◽

pp. 5885-5907 ◽

Cited By ~ 17

Author(s):

Shannon R. Davis ◽

Lawrence J. Pratt ◽

Houshuo Jiang

Keyword(s):

Red Sea ◽

Moisture Transport ◽

Arabian Peninsula ◽

Wrf Model ◽

Sea Breeze ◽

Lagrangian Model ◽

East African ◽

Diurnal Variability ◽

Mesoscale Convective ◽

Wind Regimes

Abstract The structure, variability, and regional connectivity of the Tokar Gap jet (TGJ) are described using WRF Model analyses and supporting atmospheric datasets from the East African–Red Sea–Arabian Peninsula (EARSAP) region during summer 2008. Sources of the TGJ’s unique quasi-diurnal nature and association with atypically high atmospheric moisture transport are traced back to larger-scale atmospheric dynamics influencing its forcing. These include seasonal shifts in the intertropical convergence zone (ITCZ), variability of the monsoon and North African wind regimes, and ties to other orographic flow patterns. Strong modulation of the TGJ by regional processes such as the desert heating cycle, wind convergence at the ITCZ surface front, and the local land–sea breeze cycle are described. Two case studies present the interplay of these influences in detail. The first of these was an “extreme” gap wind event on 12 July, in which horizontal velocities in the Tokar Gap exceeded 26 m s−1 and the flow from the jet extended the full width of the Red Sea basin. This event coincided with development of a large mesoscale convective complex (MCC) and precipitation at the entrance of the Tokar Gap as well as smaller gaps downstream along the Arabian Peninsula. More typical behavior of the TGJ during the 2008 summer is discussed using a second case study on 19 July. Downwind impact of the TGJ is evaluated using Lagrangian model trajectories and analysis of the lateral moisture fluxes (LMFs) during jet events. These results suggest means by which TGJ contributes to large LMFs and has potential bearing upon Sahelian rainfall and MCC development.

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Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

Annales Geophysicae ◽

10.5194/angeo-25-597-2007 ◽

2007 ◽

Vol 25 (3) ◽

pp. 597-622 ◽

Cited By ~ 5

Author(s):

F. Saïd ◽

A. Brut ◽

B. Campistron ◽

F. Cousin

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Lower Layer ◽

Lower Troposphere ◽

Sea Breeze ◽

Transport Processes ◽

Topographic Effects ◽

Pollution Transport ◽

Data Set ◽

Diurnal Variability

Abstract. This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL) development during two specific meteorological conditions of the second Intensive Observation Period (IOP). The first situation (IOP2a, from 22 June to 23 June) corresponds to moderate, dry and cold northerly winds (end of Mistral event), coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June). In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.

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Extent of diurnal cycle of rainfall and its intra seasonal variation over coastal Tamil Nadu during north east monsoon season

MAUSAM ◽

10.54302/mausam.v73i1.4984 ◽

2022 ◽

Vol 73 (1) ◽

pp. 1-18

Author(s):

Y.E.A. RAJ ◽

B. AMUDHA

Keyword(s):

Diurnal Variation ◽

Diurnal Cycle ◽

Tamil Nadu ◽

Monsoon Season ◽

Statistical Significance ◽

Early Morning ◽

Rainfall Anomaly ◽

Land Breeze ◽

North East ◽

Hourly Rainfall

The diurnal variation of north east monsoon rainfall of coastal Tamil Nadu represented by four coastal stations Chennai Nungambakkam (Nbk), Chennai Meenambakkam (Mbk), Nagapattinam (Npt) and Pamban (Pbn) was studied in detail based on hourly rainfall data of rainy days only, for the period 1 Oct-31 Dec for the 47/48 year period 1969-2016/2017. Mean Octet rainfall and its anomaly were computed for the 8 octets 00-03,…., 21-24 hrs of the day and the anomaly was tested for statistical significance. Various analysis for the individual months of Oct, Nov, Dec and the entire period Oct-Dec were separately conducted. The basic technique of evolutionary histogram analysis supplemented by harmonic analysis of octet mean rainfall anomaly was used to detect the diurnal cycle signal. Two indices named as diurnal variation of rainfall index and coefficient of mean absolute octet rainfall anomaly representing the intensity of diurnal variation in dimensionless numbers were defined, computed and interpreted. The analysis based on the above techniques revealed that the diurnal signal which shows an early morning maximum and late afternoon minimum of octet rainfall is well defined in Oct, decreases in Nov and further decreases in Dec for all the 4 stations. Though the diurnal variation manifests a well defined pattern in Dec the signal is not statistically significant in most cases. For Nbk and Mbk there is a weak secondary peak of octet rainfall anomaly occurring in the forenoon and afternoon respectively in Oct and Dec suggesting the presence of semi-diurnal variation of rainfall. Stationwise, the diurnal signal is most well defined for each month/season in Pbn followed by Npt, Nbk and then Mbk. The physical causes behind the diurnal signal and its decrease as the north east monsoon season advances from Oct to Dec have been deliberated. The well known feature of nocturnal maximum of oceanic convection influencing a coastal station with maritime climate and the higher saturation at the lower levels of the upper atmosphere in the early morning hours have been advanced as some of the causes. For the much more complex feature of decrease of diurnal signal with the advancement of the season, the decrease of minimum surface temperature over coastal Tamil Nadu from Oct to Dec causing an early morning conceptual land breeze has been shown as one of the plausible causes based on analysis of temperature and wind. Scope for further work based on data from automatic weather stations, weather satellites and Doppler Weather Radars has been discussed.

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Evaluating the diurnal cycle of South Atlantic stratocumulus clouds as observed by MSG SEVIRI

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-13283-2018 ◽

2018 ◽

Vol 18 (17) ◽

pp. 13283-13304 ◽

Cited By ~ 4

Author(s):

Chellappan Seethala ◽

Jan Fokke Meirink ◽

Ákos Horváth ◽

Ralf Bennartz ◽

Rob Roebeling

Keyword(s):

Diurnal Variation ◽

Biomass Burning ◽

Diurnal Cycle ◽

Near Infrared ◽

South Atlantic ◽

Radiation Budget ◽

Ozone Monitoring Instrument ◽

Slow Increase ◽

Diurnal Variability ◽

Late Afternoon

Abstract. Marine stratocumulus (Sc) clouds play an essential role in the earth radiation budget. Here, we compare liquid water path (LWP), cloud optical thickness (τ), and cloud droplet effective radius (re) retrievals from 2 years of collocated Spinning Enhanced Visible and Infrared Imager (SEVIRI), Moderate Resolution Imaging Spectroradiometer (MODIS), and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) observations; estimate the effect of biomass burning smoke on passive imager retrievals; and evaluate the diurnal cycle of South Atlantic marine Sc clouds.The effect of absorbing aerosols from biomass burning on the retrievals was investigated using the aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI). SEVIRI and MODIS LWPs were found to decrease with increasing AI relative to TMI LWP, consistent with well-known negative visible/near-infrared (VIS/NIR) retrieval biases in τ and re. In the aerosol-affected months of July–August–September, SEVIRI LWP – based on the 1.6 µm re – was biased low by 14 g m−2 ( ∼ 16 %) compared to TMI in overcast scenes, while MODIS LWP showed a smaller low bias of 4 g m−2 ( ∼ 5 %) for the 1.6 µm channel and a high bias of 8 g m−2 ( ∼ 10 %) for the 3.7 µm channel compared to TMI. Neglecting aerosol-affected pixels reduced the mean SEVIRI–TMI LWP bias considerably. For 2 years of data, SEVIRI LWP had a correlation with TMI and MODIS LWP of about 0.86 and 0.94, respectively, and biases of only 4–8 g m−2 (5 %–10 %) for overcast cases.The SEVIRI LWP diurnal cycle was in good overall agreement with TMI except in the aerosol-affected months. Both TMI and SEVIRI LWP decreased from morning to late afternoon, after which a slow increase was observed. Terra and Aqua MODIS mean LWPs also suggested a similar diurnal variation. The relative amplitude of the 2-year-mean and seasonal-mean LWP diurnal cycle varied between 35 % and 40 % from morning to late afternoon for overcast cases. The diurnal variation in SEVIRI LWP was mainly due to changes in τ, while re showed only little diurnal variability.

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