scholarly journals Spatial Variability of the Background Diurnal Cycle of Deep Convection around the GoAmazon2014/5 Field Campaign Sites

2016 ◽  
Vol 55 (7) ◽  
pp. 1579-1598 ◽  
Author(s):  
Casey D. Burleyson ◽  
Zhe Feng ◽  
Samson M. Hagos ◽  
Jerome Fast ◽  
Luiz A. T. Machado ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Satellite Data ◽  
Diurnal Cycle ◽  
Anthropogenic Impacts ◽  
Deep Convection ◽  
Sea Breeze ◽  
Spatial And Temporal Variability ◽  
Trade Winds ◽  
Diurnal Cycles ◽  
Negro River

AbstractThe isolation of the Amazon rain forest makes it challenging to observe precipitation forming there, but it also creates a natural laboratory to study anthropogenic impacts on clouds and precipitation in an otherwise pristine environment. Observations were collected upwind and downwind of Manaus, Brazil, during the “Observations and Modeling of the Green Ocean Amazon 2014–2015” experiment (GoAmazon2014/5). Besides aircraft, most of the observations were point measurements made in a spatially heterogeneous environment, making it hard to distinguish anthropogenic signals from naturally occurring spatial variability. In this study, 15 years of satellite data are used to examine the spatial and temporal variability of deep convection around the GoAmazon2014/5 sites using cold cloud tops (infrared brightness temperatures colder than 240 K) as a proxy for deep convection. During the rainy season, convection associated with the inland propagation of the previous day’s sea-breeze front is in phase with the diurnal cycle of deep convection near Manaus but is out of phase a few hundred kilometers to the east and west. Convergence between the river breezes and the easterly trade winds generates afternoon convection up to 10% more frequently (on average ~4 mm day−1 more intense rainfall) at the GoAmazon2014/5 sites east of the Negro River (T0e, T0t/k, and T1) relative to the T3 site, which was located west of the river. In general, the annual and diurnal cycles of precipitation during 2014 were similar to climatological values that are based on satellite data from 2000 to 2013.

Diurnal Cycles of Synthetic Microwave Sounding Lower-Stratospheric Temperatures from Radio Occultation Observations, Reanalysis, and Model Simulations

2021 ◽  
Author(s):  
Aodhan J Sweeney ◽  
Qiang Fu
Keyword(s):  
Diurnal Cycle ◽  
Radio Occultation ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Winter Season ◽  
Boreal Winter ◽  
Diurnal Cycles ◽  
Stratospheric Temperature ◽  
Diurnal Range ◽  
Microwave Sounding

AbstractAn observationally-based global climatology of the temperature diurnal cycle in the lower stratosphere is derived from eleven different satellites with Global Positioning System-Radio Occultation (GPS-RO) measurements from 2006-2020. Methods used in our analysis allow for accurate characterization of global stratospheric temperature diurnal cycles, even in the high latitudes where the diurnal signal is small but longer timescale variability is large. A climatology of the synthetic Microwave Sounding Unit (MSU) and Advanced MSU (AMSU) Temperature in the Lower Stratosphere (TLS) is presented to assess the accuracy of diurnal cycle climatologies for the MSU and AMSU TLS observations, which have traditionally been generated by model data. The TLS diurnal temperature ranges are typically less than 0.4 K in all latitude bands and seasons investigated. It is shown that the diurnal range (maximum minus minimum temperature) of TLS is largest over southern hemisphere tropical land in the boreal winter season, indicating the important role of deep convection. The range, phase, and seasonality of the TLS diurnal cycle are generally well captured by the WACCM6 simulation and ERA5 reanalysis. We also present an observationally-based diurnal cycle climatology of temperature profiles from 300-10 hPa for various latitude bands and seasons and compare the ERA5 reanalysis with the observations.

scholarly journals The Amazon Dense GNSS Meteorological Network: A New Approach for Examining Water Vapor and Deep Convection Interactions in the Tropics

2015 ◽  
Vol 96 (12) ◽  
pp. 2151-2165 ◽  
Author(s):  
David K. Adams ◽  
Rui M. S. Fernandes ◽  
Kirk L. Holub ◽  
Seth I. Gutman ◽  
Henrique M. J. Barbosa ◽  
...  
Keyword(s):  
Water Vapor ◽  
Diurnal Cycle ◽  
Numerical Models ◽  
Deep Convection ◽  
Precipitable Water ◽  
Sea Breeze ◽  
Tropical Meteorology ◽  
Precipitable Water Vapor ◽  
Gnss Meteorology ◽  
The Tropics

Abstract The complex interactions between water vapor fields and deep atmospheric convection remain one of the outstanding problems in tropical meteorology. The lack of high spatial–temporal resolution, all-weather observations in the tropics has hampered progress. Numerical models have difficulties, for example, in representing the shallow-to-deep convective transition and the diurnal cycle of precipitation. Global Navigation Satellite System (GNSS) meteorology, which provides all-weather, high-frequency (5 min), precipitable water vapor estimates, can help. The Amazon Dense GNSS Meteorological Network experiment, the first of its kind in the tropics, was created with the aim of examining water vapor and deep convection relationships at the mesoscale. This innovative, Brazilian-led international experiment consisted of two mesoscale (100 km × 100 km) networks: 1) a 1-yr (April 2011–April 2012) campaign (20 GNSS meteorological sites) in and around Manaus and 2) a 6-week (June 2011) intensive campaign (15 GNSS meteorological sites) in and around Belem, the latter in collaboration with the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (CHUVA) Project in Brazil. Results presented here from both networks focus on the diurnal cycle of precipitable water vapor associated with sea-breeze convection in Belem and seasonal and topographic influences in and around Manaus. Ultimately, these unique observations may serve to initialize, constrain, or validate precipitable water vapor in high-resolution models. These experiments also demonstrate that GNSS meteorology can expand into logistically difficult regions such as the Amazon. Other GNSS meteorology networks presently being constructed in the tropics are summarized.

scholarly journals Diurnal Cycle of Surface Winds in the Maritime Continent Observed through Satellite Scatterometry

2019 ◽  
Vol 147 (6) ◽  
pp. 2023-2044 ◽  
Author(s):  
Ewan Short ◽  
Claire L. Vincent ◽  
Todd P. Lane
Keyword(s):  
Diurnal Cycle ◽  
Surface Wind ◽  
Sea Breeze ◽  
Surface Winds ◽  
Time Data ◽  
Maritime Continent ◽  
Sea Breezes ◽  
Diurnal Cycles ◽  
Using Data ◽  
Precipitation Cycles

Abstract The diurnal cycle of surface winds throughout the Maritime Continent plays a significant role in the formation of precipitation over the islands of the region and over the surrounding seas. This study investigates the connection between the diurnal cycles of surface wind and offshore precipitation using data from four satellite scatterometer instruments and two satellite precipitation radar instruments. For the first time, data from three scatterometer instruments are combined to yield a more temporally complete picture of the surface wind diurnal cycles over the Maritime Continent’s surrounding seas. The results indicate that land–sea breezes typically propagate over 400 km offshore, produce mean wind perturbations of between 1 and 5 m s−1, and propagate as gravity waves at 25–30 m s−1. Diurnal precipitation cycles are affected through gravity wave propagation processes associated with the land–sea breezes, and through the convergence of land breezes from nearby islands. These observational results are then compared with previous mesoscale modeling results. It is shown that land–sea breezes occur too early, and are too intense in these modeling results, and this may partly explain why these modeling results also exhibit an early, overly intense diurnal precipitation cycle. This study also investigates variations in the diurnal cycle of surface winds at seasonal and intraseasonal time scales. Previous work has suggested that seasonal and intraseasonal variations in surface heating affect the land–sea breeze circulation and diurnal precipitation cycles; we argue that variations in background winds also play a defining role in modulating coastally influenced local winds.

scholarly journals Diurnal cycle of precipitation and near-surface atmospheric conditions over the maritime continent: land–sea contrast and impacts of ambient winds in cloud-permitting simulations

2021 ◽  
Author(s):  
Yuntao Wei ◽  
Zhaoxia Pu
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Deep Convection ◽  
Vertical Motion ◽  
Sea Breeze ◽  
Return Flow ◽  
Atmospheric Conditions ◽  
Maritime Continent ◽  
Regional Variability ◽  
Near Surface

AbstractA set of cloud-permitting-scale numerical simulations during January–February 2018 is used to examine the diurnal cycle (DC) of precipitation and near-surface variables (e.g., 2 m temperature, 10 m wind and convergence) over the Indo-Pacific Maritime Continent under the impacts of shore-orthogonal ambient winds (SOAWs). It is found that the DC of these variables and their variabilities of daily maxima, minima, and diurnal amplitudes vary over land, sea, and coastal regions. Among all variables, the DC of precipitation has the highest linear correlation with near-surface convergence (near-surface temperature) over coastal (noncoastal) regions. The correlations among the DCs of precipitation, wind, and heating are greater over the ocean than over land. Sine curves can model accurately the DCs of most variables over the ocean, but not over land. SOAWs act to influence the DC mainly by affecting the diurnal amplitude of the considered variables, with DC being stronger under more strengthened offshore SOAWs, though variable dependence and regional variability exist. Composite analysis over Sumatra reveals that under weak SOAWs, shallow clouds are dominant and cause a pre-moistening effect, supporting shallow-to-deep convection transition. A sea breeze circulation (SBC) with return flow aloft can develop rapidly. Cold pools are better able to trigger new updrafts and contribute to the upscale growth and inland migration of deep convection. In addition, warm gravity waves can propagate upward throughout the troposphere, thereby supporting a strong DC. In contrast, under strong SOAWs, both shallow and middle-high clouds prevail and persist throughout the day. The evolution of moistening and SBC is reduced, leading to weak variation in vertical motion and rainwater confined to the boundary layer. Large-scale winds, moisture, and convection are discussed to interpret how strong SOAWs affect the DC of Sumatra.

scholarly journals The Impact of MJO, Kelvin, and Equatorial Rossby Waves on the Diurnal Cycle over the Maritime Continent

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 711
Author(s):  
Lakemariam Worku ◽  
Ademe Mekonnen ◽  
Carl Schreck
Keyword(s):  
Diurnal Cycle ◽  
Deep Convection ◽  
Kelvin Waves ◽  
Kelvin Wave ◽  
Maritime Continent ◽  
Diurnal Cycles ◽  
Precipitation Analysis ◽  
The Impact ◽  
Convection Dominated ◽  
Equatorial Rossby Waves

The impacts of the Madden–Julian Oscillation (MJO), Kelvin waves, and Equatorial Rossby (ER) waves on the diurnal cycle of rainfall and types of deep convection over the Maritime Continent are investigated using rainfall from the Tropical Rainfall Measurement Mission Multisatellite Precipitation Analysis and Infrared Weather States (IR–WS) data from the International Satellite Cloud Climatology Project. In an absolute sense, the MJO produced its strongest modulations of rainfall and organized deep convection over the islands, when and where convection is already strongest. The MJO actually has a greater percentage modulation over the coasts and seas, but it does not affect weaker diurnal cycle there. Isolated deep convection was also more prevalent over land during the suppressed phase, while organized deep convection dominated the enhanced phase, consistent with past work. This study uniquely examined the effects of Kelvin and ER waves on rainfall, convection, and their diurnal cycles over the Maritime Continent. The modulation of convection by Kelvin waves closely mirrored that by the MJO, although the Kelvin wave convection continued farther into the decreasing phase. The signals for ER waves were also similar but less distinct. An improved understanding of how these waves interact with convection could lead to improved subseasonal forecast skill.

Submesoscale Spatiotemporal Variability of North American Monsoon Rainfall over Complex Terrain

2007 ◽  
Vol 20 (9) ◽  
pp. 1751-1773 ◽  
Author(s):  
Mekonnen Gebremichael ◽  
Enrique R. Vivoni ◽  
Christopher J. Watts ◽  
Julio C. Rodríguez
Keyword(s):  
Spatial Pattern ◽  
Diurnal Cycle ◽  
North American ◽  
Rainfall Intensity ◽  
Temporal Dynamics ◽  
Spatiotemporal Variability ◽  
North American Monsoon ◽  
Spatial And Temporal Variability ◽  
Study Region ◽  
Diurnal Cycles

Abstract The authors analyze information from rain gauges, geostationary infrared satellites, and low earth orbiting radar in order to describe and characterize the submesoscale (<75 km) spatial pattern and temporal dynamics of rainfall in a 50 km × 75 km study area located in Sonora, Mexico, in the periphery of the North American monsoon system core region. The temporal domain spans from 1 July to 31 August 2004, corresponding to one monsoon season. Results reveal that rainfall in the study region is characterized by high spatial and temporal variability, strong diurnal cycles in both frequency and intensity with maxima in the evening hours, and multiscaling behavior in both temporal and spatial fields. The scaling parameters of the spatial rainfall fields exhibit dependence on the rainfall rate at the synoptic scale. The rainfall intensity exhibits a slightly stronger diurnal cycle compared to the rainfall frequency, and the maximum lag time between the two diurnal peaks is within 2.4 h, with earlier peaks observed for rainfall intensity. The time of maximum cold cloud occurrence does not vary with the infrared threshold temperature used (215–235 K), while the amplitude of the diurnal cycle varies in such a way that deep convective cells have stronger diurnal cycles. Furthermore, the results indicate that the diurnal cycle of cold cloud occurrence can be used as a surrogate for some basic features of the diurnal cycle of rainfall. The spatial pattern and temporal dynamics of rainfall are modulated by topographic features and large-scale features (circulation and moisture fields as related to geographical location). As compared to valley areas, mountainous areas are characterized by an earlier diurnal peak, an earlier date of maximum precipitation, closely clustered rainy hours, frequent yet small rainfall events, and less dependence of precipitation accumulation on elevation. As compared to the northern section of the study area, the southern section is characterized by strong convective systems that peak late diurnally. The results of this study are important for understanding the physical processes involved, improving the representation of submesoscale variability in models, downscaling rainfall data from coarse meteorological models to smaller hydrological scales, and interpreting and validating remote sensing rainfall estimates.

scholarly journals Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 868
Author(s):  
Jonathan Durand ◽  
Edouard Lees ◽  
Olivier Bousquet ◽  
Julien Delanoë ◽  
François Bonnardot
Keyword(s):  
Sea Breeze ◽  
Satellite System ◽  
Research Infrastructure ◽  
Weather Data ◽  
Reunion Island ◽  
Wet Season ◽  
Trade Winds ◽  
Cloud Radar ◽  
Réunion Island ◽  
Global Navigation Satellite

In November 2016, a 95 GHz cloud radar was permanently deployed in Reunion Island to investigate the vertical distribution of tropical clouds and monitor the temporal variability of cloudiness in the frame of the pan-European research infrastructure Aerosol, Clouds and Trace gases Research InfraStructure (ACTRIS). In the present study, reflectivity observations collected during the two first years of operation (2016–2018) of this vertically pointing cloud radar are relied upon to investigate the diurnal and seasonal cycle of cloudiness in the northern part of this island. During the wet season (December–March), cloudiness is particularly pronounced between 1–3 km above sea level (with a frequency of cloud occurrence of 45% between 12:00–19:00 LST) and 8–12 km (with a frequency of cloud occurrence of 15% between 14:00–19:00 LST). During the dry season (June–September), this bimodal vertical mode is no longer observed and the vertical cloud extension is essentially limited to a height of 3 km due to both the drop-in humidity resulting from the northward migration of the ITCZ and the capping effect of the trade winds inversion. The frequency of cloud occurrence is at its maximum between 13:00–18:00 LST, with a probability of 35% at 15 LST near an altitude of 2 km. The analysis of global navigation satellite system (GNSS)-derived weather data also shows that the diurnal cycle of low- (1–3 km) and mid-to-high level (5–10 km) clouds is strongly correlated with the diurnal evolution of tropospheric humidity, suggesting that additional moisture is advected towards the island by the sea breeze regime. The detailed analysis of cloudiness observations collected during the four seasons sampled in 2017 and 2018 also shows substantial differences between the two years, possibly associated with a strong positive Indian Ocean Southern Dipole (IOSD) event extending throughout the year 2017.

scholarly journals The diurnal cycle of cloud profiles over land and ocean between 51° S and 51° N, seen by the CATS spaceborne lidar from the International Space Station

2018 ◽  
Vol 18 (13) ◽  
pp. 9457-9473 ◽  
Author(s):  
Vincent Noel ◽  
Hélène Chepfer ◽  
Marjolaine Chiriaco ◽  
John Yorks
Keyword(s):  
High Altitude ◽  
International Space Station ◽  
Diurnal Cycle ◽  
Space Station ◽  
Cloud Fraction ◽  
Vertical Profiles ◽  
Diurnal Variability ◽  
International Space ◽  
Low Level ◽  
Diurnal Cycles

Abstract. We document, for the first time, how detailed vertical profiles of cloud fraction (CF) change diurnally between 51∘ S and 51∘ N, by taking advantage of 15 months of measurements from the Cloud-Aerosol Transport System (CATS) lidar on the non-sun-synchronous International Space Station (ISS). Over the tropical ocean in summer, we find few high clouds during daytime. At night they become frequent over a large altitude range (11–16 km between 22:00 and 04:00 LT). Over the summer tropical continents, but not over ocean, CATS observations reveal mid-level clouds (4–8 km above sea level or a.s.l.) persisting all day long, with a weak diurnal cycle (minimum at noon). Over the Southern Ocean, diurnal cycles appear for the omnipresent low-level clouds (minimum between noon and 15:00) and high-altitude clouds (minimum between 08:00 and 14:00). Both cycles are time shifted, with high-altitude clouds following the changes in low-altitude clouds by several hours. Over all continents at all latitudes during summer, the low-level clouds develop upwards and reach a maximum occurrence at about 2.5 km a.s.l. in the early afternoon (around 14:00). Our work also shows that (1) the diurnal cycles of vertical profiles derived from CATS are consistent with those from ground-based active sensors on a local scale, (2) the cloud profiles derived from CATS measurements at local times of 01:30 and 13:30 are consistent with those observed from CALIPSO at similar times, and (3) the diurnal cycles of low and high cloud amounts (CAs) derived from CATS are in general in phase with those derived from geostationary imagery but less pronounced. Finally, the diurnal variability of cloud profiles revealed by CATS strongly suggests that CALIPSO measurements at 01:30 and 13:30 document the daily extremes of the cloud fraction profiles over ocean and are more representative of daily averages over land, except at altitudes above 10 km where they capture part of the diurnal variability. These findings are applicable to other instruments with local overpass times similar to CALIPSO's, such as all the other A-Train instruments and the future EarthCARE mission.

scholarly journals Sources of black carbon aerosols in South Asia and surrounding regions during the Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB)

2015 ◽  
Vol 15 (10) ◽  
pp. 5415-5428 ◽  
Author(s):  
R. Kumar ◽  
M. C. Barth ◽  
V. S. Nair ◽  
G. G. Pfister ◽  
S. Suresh Babu ◽  
...  
Keyword(s):  
Spatial Variability ◽  
South Asia ◽  
Black Carbon ◽  
Biomass Burning ◽  
Regional Scale ◽  
Anthropogenic Sources ◽  
Radiation Budget ◽  
Anthropogenic Emissions ◽  
Spatial And Temporal Variability ◽  
Mass Concentrations

Abstract. This study examines differences in the surface black carbon (BC) aerosol loading between the Bay of Bengal (BoB) and the Arabian Sea (AS) and identifies dominant sources of BC in South Asia and surrounding regions during March–May 2006 (Integrated Campaign for Aerosols, Gases and Radiation Budget, ICARB) period. A total of 13 BC tracers are introduced in the Weather Research and Forecasting Model coupled with Chemistry to address these objectives. The model reproduced the temporal and spatial variability of BC distribution observed over the AS and the BoB during the ICARB ship cruise and captured spatial variability at the inland sites. In general, the model underestimates the observed BC mass concentrations. However, the model–observation discrepancy in this study is smaller compared to previous studies. Model results show that ICARB measurements were fairly well representative of the AS and the BoB during the pre-monsoon season. Elevated BC mass concentrations in the BoB are due to 5 times stronger influence of anthropogenic emissions on the BoB compared to the AS. Biomass burning in Burma also affects the BoB much more strongly than the AS. Results show that anthropogenic and biomass burning emissions, respectively, accounted for 60 and 37% of the average ± standard deviation (representing spatial and temporal variability) BC mass concentration (1341 ± 2353 ng m−3) in South Asia. BC emissions from residential (61%) and industrial (23%) sectors are the major anthropogenic sources, except in the Himalayas where vehicular emissions dominate. We find that regional-scale transport of anthropogenic emissions contributes up to 25% of BC mass concentrations in western and eastern India, suggesting that surface BC mass concentrations cannot be linked directly to the local emissions in different regions of South Asia.

scholarly journals The Diurnal Cycle of Cloud-Top Height and Cloud Cover over the Southeastern Pacific as Observed by GOES-10

2013 ◽  
Vol 70 (8) ◽  
pp. 2393-2408 ◽  
Author(s):  
David Painemal ◽  
Patrick Minnis ◽  
Larry O'Neill
Keyword(s):  
Boundary Layer ◽  
Mixed Boundary ◽  
Phase Speed ◽  
Tropical Rainfall Measuring Mission ◽  
Sea Breeze ◽  
Air Entrainment ◽  
Liquid Water Path ◽  
Diurnal Cycles ◽  
Southeastern Pacific ◽  
Microwave Imager

Abstract The diurnal cycles in cloud-top height Htop and cloud fraction (CF) in the southeastern Pacific stratocumulus region were determined for October–November 2008 by analyzing data from Geostationary Operational Environmental Satellite-10 (GOES-10) according to a diurnal/semidiurnal harmonic fitting technique. The value of Htop was obtained by applying a formula based on a linear regression of the differences between GOES-10 cloud-top temperature and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) satellite sea surface temperature, with a common 0.25° × 0.25° spatial resolution. A satellite liquid water path (LWP) climatology complemented this dataset. Southwestward transects of Htop and LWP anomalies reveal a coherent propagating signal from the coast in the afternoon, with a typical phase speed of 25 m s−1. This pattern is preceded by a subsidence wave that reaches its peak a few hours before the maximum in Htop and LWP anomalies. Coincident increases in LWP and Htop after the subsidence wave passes suggest that the boundary layer deepening promotes cloud thickening and increased LWP, which are likely maintained through a well-mixed boundary layer and sufficient moisture fluxes that can counteract the effect of dry air entrainment. The interference between the radiatively and subsidence wave–driven cycles gives rise to a semidiurnal cycle in Htop along the coast. While the semidiurnal amplitude is near 80 m close to the coast with a fraction of explained variance greater than 0.4, it decreases to 30 m offshore (80°W). Similar to Htop, CF also exhibits contrasting zonal differences, but with a smaller semidiurnal component. The phase of the semidiurnal harmonic resembles the subsidence propagation westward, and the noticeable land–sea breeze circulation at 26°S that extends 200 km offshore.

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