Impact of deep convection on the isotopic amount effect in tropical precipitation

2017 ◽  
Vol 122 (3) ◽  
pp. 1505-1523 ◽  
Author(s):  
Thejna Tharammal ◽  
Govindasamy Bala ◽  
David Noone
Keyword(s):  
Deep Convection ◽  
Tropical Precipitation ◽  
Amount Effect

scholarly journals Tropical Precipitation Extremes

2013 ◽  
Vol 26 (4) ◽  
pp. 1457-1466 ◽  
Author(s):  
William B. Rossow ◽  
Ademe Mekonnen ◽  
Cindy Pearl ◽  
Weber Goncalves
Keyword(s):  
Large Scale ◽  
Accumulation Rate ◽  
Deep Convection ◽  
Circulation Model ◽  
Grid Cell ◽  
Precipitation Intensity ◽  
Convective Systems ◽  
Tropical Precipitation ◽  
Cloud Properties ◽  
Deep Convective Systems

Abstract Classifying tropical deep convective systems by the mesoscale distribution of their cloud properties and sorting matching precipitation measurements over an 11-yr period reveals that the whole distribution of instantaneous precipitation intensity and daily average accumulation rate is composed of (at least) two separate distributions representing distinctly different types of deep convection associated with different meteorological conditions (the distributions of non-deep-convective situations are also shown for completeness). The two types of deep convection produce very different precipitation intensities and occur with very different frequencies of occurrence. Several previous studies have shown that the interaction of the large-scale tropical circulation with deep convection causes switching between these two types, leading to a substantial increase of precipitation. In particular, the extreme portion of the tropical precipitation intensity distribution, above 2 mm h−1, is produced by 40% of the larger, longer-lived mesoscale-organized type of convection with only about 10% of the ordinary convection occurrences producing such intensities. When average precipitation accumulation rates are considered, essentially all of the values above 2 mm h−1 are produced by the mesoscale systems. Yet today’s atmospheric models do not represent mesoscale-organized deep convective systems that are generally larger than current-day circulation model grid cell sizes but smaller than the resolved dynamical scales and last longer than the typical physics time steps. Thus, model-based arguments for how the extreme part of the tropical precipitation distribution might change in a warming climate are suspect.

scholarly journals Reverse Engineering the Tropical Precipitation–Buoyancy Relationship

2018 ◽  
Vol 75 (5) ◽  
pp. 1587-1608 ◽  
Author(s):  
Fiaz Ahmed ◽  
J. David Neelin
Keyword(s):  
Mass Flux ◽  
Environmental Influence ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Rapid Onset ◽  
Thermodynamic Structure ◽  
Tropical Precipitation ◽  
Flux Profile ◽  
Vertical Variations ◽  
The Tropics

The tropical precipitation–moisture relationship, characterized by rapid increases in precipitation for modest increases in moisture, is conceptually recast in a framework relevant to plume buoyancy and conditional instability in the tropics. The working hypothesis in this framework links the rapid onset of precipitation to integrated buoyancy in the lower troposphere. An analytical expression that relates the buoyancy of an entraining plume to the vertical thermodynamic structure is derived. The natural variables in this framework are saturation and subsaturation equivalent potential temperatures, which capture the leading-order temperature and moisture variations, respectively. The use of layer averages simplifies the analytical and subsequent numerical treatment. Three distinct layers, the boundary layer, the lower free troposphere, and the midtroposphere, adequately capture the vertical variations in the thermodynamic structure. The influence of each environmental layer on the plume is assumed to occur via lateral entrainment, corresponding to an assumed mass-flux profile. The fractional contribution of each layer to the midlevel plume buoyancy (i.e., the layer weight) is estimated from TRMM 3B42 precipitation and ERA-Interim thermodynamic profiles. The layer weights are used to “reverse engineer” a deep-inflow mass-flux profile that is nominally descriptive of the tropical atmosphere through the onset of deep convection. The layer weights—which are nearly the same for each of the layers—constitute an environmental influence function and are also used to compute a free-tropospheric integrated buoyancy measure. This measure is shown to be an effective predictor of onset in conditionally averaged precipitation across the global tropics—over both land and ocean.

scholarly journals Seasonal Dependency of Tropical Precipitation Change under Global Warming

2020 ◽  
Vol 33 (18) ◽  
pp. 7897-7908 ◽  
Author(s):  
Yu-Fan Geng ◽  
Shang-Ping Xie ◽  
Xiao-Tong Zheng ◽  
Chuan-Yang Wang
Keyword(s):  
Global Warming ◽  
Deep Convection ◽  
Atmospheric Model ◽  
Precipitation Change ◽  
Dynamic Component ◽  
Tropical Precipitation ◽  
Eastern Equatorial Pacific ◽  
Warming Pattern ◽  
Sst Warming ◽  
Dynamic Components

AbstractTropical precipitation change under global warming varies with season. The present study investigates the characteristics and cause of the seasonality in rainfall change. Diagnostically, tropical precipitation change is decomposed into thermodynamic and dynamic components. The thermodynamic component represents the wet-get-wetter effect and its seasonality is due mostly to that in the mean vertical velocity, especially in the monsoon regions. The dynamic component includes the warmer-get-wetter effect due to the spatial variations in sea surface temperature (SST) warming, while the seasonality is due to that of the climatological SST and can be largely reproduced by an atmospheric model forced with the monthly climatological SST plus the annual-mean SST warming pattern. In the eastern equatorial Pacific where the SST warming is locally enhanced; for example, rainfall increases only during the March–May season when the climatological SST is high enough for deep convection. To the extent that the seasonality of tropical precipitation change over oceans arises mostly from that of the climatological SST, the results support the notion that reducing model biases in climatology improves regional rainfall projections.

scholarly journals Simple Multicloud Models for the Diurnal Cycle of Tropical Precipitation. Part I: Formulation and the Case of the Tropical Oceans

2011 ◽  
Vol 68 (10) ◽  
pp. 2169-2190 ◽  
Author(s):  
Yevgeniy Frenkel ◽  
Boualem Khouider ◽  
Andrew J. Majda
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Deep Convection ◽  
Potential Temperature ◽  
Bowen Ratio ◽  
Tropical Convection ◽  
Heat Fluxes ◽  
Tropical Precipitation ◽  
Shallow Cumulus ◽  
Early Afternoon

Abstract The variation of tropical precipitation due to the diurnal cycle of solar heating is examined here in the context of two simple models for tropical convection. The models utilize three cloud types—congestus, deep, and stratiform—that are believed to characterize organized tropical convection and are based on the two first baroclinic modes of vertical structure plus a boundary layer mode. The two models differ mainly in the way they treat the boundary layer dynamics. The first one is purely thermodynamical and is reduced to a single equation for the equivalent potential temperature θe connecting the boundary layer to the upper troposphere through downdrafts and to the surface through evaporation while the second uses full bulk boundary layer (FBBL) dynamics with a careful separation between sensible and latent heat fluxes and parameterization of nonprecipitating shallow cumulus. It turns out that in the case of the precipitation over the ocean where the Bowen ratio is small, both models yield a qualitatively similar solution, characterized by an overnight initiation and early morning peak in precipitation consistent with observations. The modeled diurnal cycle of precipitation over the ocean is divided into four cyclic phases: 1) a CAPE (re)generation phase characterized by the enhancement of the boundary layer θe and moisture fluxes during midday and early afternoon that is followed by 2) a (re)moistening phase dominated by congestus heating during the late afternoon and moistening from downdrafts (due to detrainment of shallow cumulus, specifically in the FBBL model) and radiative cooling that lasts until midnight. 3) Deep convection is initiated around midnight when the midtroposphere is sufficiently moist and cool and (re)establishes the precipitation level near its radiative convective equilibrium (1 K day−1) and then 4) peaks with sunrise at 0600 LST to yield a precipitation maximum of roughly 2 K day−1 at around 0900 LST that dries the troposphere and consumes CAPE and closes the cycle.

Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin

1998 ◽  
Vol 180 ◽  
pp. 163-167
Author(s):  
Antoon Kuijpers ◽  
Jørn Bo Jensen ◽  
Simon R . Troelstra ◽  
And shipboard scientific party of RV Professor Logachev and RV Dana
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
Conveyor Belt ◽  
Water Masses ◽  
Labrador Sea ◽  
Greenland Sea ◽  
The North ◽  
Denmark Strait ◽  
The North Atlantic

Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

Les tempêtes de fin d'hiver 2020

2020 ◽  
pp. 089
Author(s):  
Michael Kreitz
Keyword(s):  
Conceptual Models ◽  
Deep Convection

La fin de l'hiver 2019-2020 est marquée par la succession de tempêtes. Les zones de vents forts répondent à des schémas conceptuels très différent : jet de basses couches, jet en air froid, sting jet, forte instabilité et tempête de pente aval. The end of winter 2019-2020 is characterised by successive windstorms. The areas of severe winds correspond to various conceptual models: warm jet, cold jet, sting jet, deep convection and downslope windstorm.

scholarly journals Dipole patterns in tropical precipitation were pervasive across landmasses throughout Marine Isotope Stage 5

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Katrina Nilsson-Kerr ◽  
Pallavi Anand ◽  
Philip B. Holden ◽  
Steven C. Clemens ◽  
Melanie J. Leng
Keyword(s):  
Large Scale ◽  
Marine Isotope Stage ◽  
Convergence Zone ◽  
Inter Tropical Convergence Zone ◽  
Tropical Regions ◽  
Tropical Precipitation ◽  
Rainfall Patterns ◽  
Marine Isotope Stage 5 ◽  
Climate Cooling ◽  
The Tropics

AbstractMost of Earth’s rain falls in the tropics, often in highly seasonal monsoon rains, which are thought to be coupled to the inter-hemispheric migrations of the Inter-Tropical Convergence Zone in response to the seasonal cycle of insolation. Yet characterization of tropical rainfall behaviour in the geologic past is poor. Here we combine new and existing hydroclimate records from six large-scale tropical regions with fully independent model-based rainfall reconstructions across the last interval of sustained warmth and ensuing climate cooling between 130 to 70 thousand years ago (Marine Isotope Stage 5). Our data-model approach reveals large-scale heterogeneous rainfall patterns in response to changes in climate. We note pervasive dipole-like tropical precipitation patterns, as well as different loci of precipitation throughout Marine Isotope Stage 5 than recorded in the Holocene. These rainfall patterns cannot be solely attributed to meridional shifts in the Inter-Tropical Convergence Zone.

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