scholarly journals Scale Analysis for Large-Scale Tropical Atmospheric Dynamics

2009 ◽  
Vol 66 (1) ◽  
pp. 159-172 ◽  
Author(s):  
Jun-Ichi Yano ◽  
Marine Bonazzola
Keyword(s):  
Asymptotic Expansion ◽  
Large Scale ◽  
Diabatic Heating ◽  
Scale Analysis ◽  
Leading Order ◽  
Wave Dynamics ◽  
Advection Term ◽  
Equatorial Wave ◽  
Balanced Dynamics ◽  
The Tropics

Abstract A systematic scale analysis is performed for large-scale dynamics over the tropics. It is identified that two regimes are competing: 1) a dynamics characterized by balance between the vertical advection term and diabatic heating in the thermodynamic equation, realized at horizontal scales less than L ∼ 103 km given a velocity scale U ∼ 10 m s−1, and 2) a linear equatorial wave dynamics modulated by convective diabatic heating, realized at scales larger than L ∼ 3 × 103 km given U ∼ 3 m s−1. Under the first dynamic regime (balanced), the system may be approximated as nondivergent to leading order in asymptotic expansion, as originally pointed out by Charney. Inherent subtleties of scale analysis at large scales for the tropical atmosphere are emphasized. The subtleties chiefly arise from a strong sensitivity of the nondimensional β parameter to the horizontal scale. This amounts to qualitatively different dynamic regimes for scales differing only by a factor of 3, as summarized above. Because any regime under asymptotic expansion may have a wider applicability than a formal scale analysis would suggest, the question of which one of the two identified regimes dominates can be answered only after extensive modeling and observational studies. Preliminary data analysis suggests that the balanced dynamics, originally proposed by Sobel, Nilsson, and Polvani, is relevant for a wider range than the strict scale analysis suggests. A rather surprising conclusion from the present analysis is a likely persistence of balanced dynamics toward scales as small as the mesoscale L ∼ 102 km. Leading-order nondivergence also becomes more likely the case for the smaller scales because otherwise the required diabatic heating rate becomes excessive compared to observations by increasing inversely proportionally with decreasing horizontal scales.

scholarly journals Bi-modal Structure and Variability of Large-Scale Diabatic Heating in the Tropics

2009 ◽  
Vol 66 (12) ◽  
pp. 3621-3640 ◽  
Author(s):  
Chidong Zhang ◽  
Samson M. Hagos
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Function Analysis ◽  
Surface Wind ◽  
Building Blocks ◽  
Wind Fields ◽  
Balanced Model ◽  
Heating Profiles ◽  
The Tropics ◽  
Rotated Empirical Orthogonal Function

Abstract Tropical diabatic heating profiles estimated using sounding data from eight field campaigns were diagnosed to document their common and prevailing structure and variability that are relevant to the large-scale circulation. The first two modes of a rotated empirical orthogonal function analysis—one deep, one shallow—explain 85% of the total variance of all data combined. These two modes were used to describe the heating evolution, which led to three composited heating profiles that are considered as prevailing large-scale heating structures. They are, respectively, shallow, bottom heavy (peak near 700 hPa); deep, middle heavy (peak near 400 hPa); and stratiform-like, top heavy (heating peak near 400 hPa and cooling peak near 700 hPa). The amplitudes and occurrence frequencies of the shallow, bottom-heavy heating profiles are comparable to those of the stratiform-like, top-heavy ones. The sequence of the most probable heating evolution is deep tropospheric cooling to bottom-heavy heating, to middle heavy heating, to stratiform-like heating, then back to deep tropospheric cooling. This heating transition appears to occur on different time scales. Each of the prevailing heating structures is interpreted as being composed of particular fractional populations of various types of precipitating cloud systems, which are viewed as the building blocks for the mean. A linear balanced model forced by the three prevailing heating profiles produces rich vertical structures in the circulation with multiple overturning cells, whose corresponding moisture convergence and surface wind fields are very sensitive to the heating structures.

Estimates of Tropical Diabatic Heating Profiles: Commonalities and Uncertainties

2010 ◽  
Vol 23 (3) ◽  
pp. 542-558 ◽  
Author(s):  
Samson Hagos ◽  
Chidong Zhang ◽  
Wei-Kuo Tao ◽  
Steve Lang ◽  
Yukari N. Takayabu ◽  
...  
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Tropical Rainfall Measuring Mission ◽  
Upper Troposphere ◽  
Tropical Oceans ◽  
Field Campaigns ◽  
Heating Profiles ◽  
The Tropics ◽  
Rain Rates

Abstract This study aims to evaluate the consistency and discrepancies in estimates of diabatic heating profiles associated with precipitation based on satellite observations and microphysics and those derived from the thermodynamics of the large-scale environment. It presents a survey of diabatic heating profile estimates from four Tropical Rainfall Measuring Mission (TRMM) products, four global reanalyses, and in situ sounding measurements from eight field campaigns at various tropical locations. Common in most of the estimates are the following: (i) bottom-heavy profiles, ubiquitous over the oceans, are associated with relatively low rain rates, while top-heavy profiles are generally associated with high rain rates; (ii) temporal variability of latent heating profiles is dominated by two modes, a deep mode with a peak in the upper troposphere and a shallow mode with a low-level peak; and (iii) the structure of the deep modes is almost the same in different estimates and different regions in the tropics. The primary uncertainty is in the amount of shallow heating over the tropical oceans, which differs substantially among the estimates.

Residual Diagnosis of Diabatic Heating from ERA-40 and NCEP Reanalyses: Intercomparisons with TRMM

2009 ◽  
Vol 22 (2) ◽  
pp. 414-428 ◽  
Author(s):  
Steven C. Chan ◽  
Sumant Nigam
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Tropical Rainfall Measuring Mission ◽  
Latent Heating ◽  
Maritime Continent ◽  
Precipitation Estimates ◽  
Trmm Precipitation ◽  
Heating Profiles ◽  
The Tropics ◽  
Heating Profile

Abstract Diabatic heating is diagnosed from the 40-yr ECMWF Re-Analysis (ERA-40) circulation as a residue in the thermodynamic equation. The heating distribution is compared with the heating structure diagnosed from NCEP and 15-yr ECMWF Re-Analysis (ERA-15) circulation and latent heating generated from Tropical Rainfall Measuring Mission (TRMM) observations using the convective–stratiform heating (CSH) algorithm. The ERA-40 residual heating in the tropics is found to be stronger than NCEP’s (and ERA-15), especially in July when its zonal–vertical average is twice as large. The bias is strongest over the Maritime Continent in January and over the eastern basins and Africa in July. Comparisons with precipitation indicate ERA-40 heating to be much more realistic over the eastern Pacific but excessive over the Maritime Continent, by at least 20% in January. Intercomparison of precipitation estimates from heating-profile integrals and station and satellite analyses reveals the TRMM CSH latent heating to be chronically weak by as much as a factor of 2! It is the low-side outlier among nine precipitation estimates in three of the four analyzed regions. No less worrisome is the inconsistency between the integral of the CSH latent heating profile in the tropics and the TRMM precipitation retrievals constraining the CSH algorithm (e.g., the 3A25 analysis). Confronting TRMM’s diagnosis of latent heating from local rainfall retrievals and local cumulus-model heating profiles with heating based on the large-scale assimilated circulation is a defining attribute of this study.

scholarly journals Diabatic Heating Profiles in Recent Global Reanalyses

2013 ◽  
Vol 26 (10) ◽  
pp. 3307-3325 ◽  
Author(s):  
Jian Ling ◽  
Chidong Zhang
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Sole Source ◽  
Cumulus Parameterization ◽  
Precipitation Process ◽  
Limited Information ◽  
Hydrological Cycles ◽  
Heating Profiles ◽  
The Tropics ◽  
Modern Era

Abstract Diabatic heating profiles are extremely important to the atmospheric circulation in the tropics and therefore to the earth’s energy and hydrological cycles. However, their global structures are poorly known because of limited information from in situ observations. Some modern global reanalyses provide the temperature tendency from the physical processes. Their proper applications require an assessment of their accuracy and uncertainties. In this study, diabatic heating profiles from three recent global reanalyses [ECMWF Interim Re-Analysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), and Modern Era Retrospective Analysis for Research and Applications (MERRA)] are compared to those derived from currently available sounding observations in the tropics and to each other in the absence of the observations. Diabatic heating profiles produced by the reanalyses match well with those based on sounding observations only at some locations. The three reanalyses agree with each other better in the extratropics, where large-scale condensation dominates the precipitation process in data assimilation models, than in the tropics, where cumulus parameterization dominates. In the tropics, they only agree with each other in gross features, such as the contrast between the ITCZs over different oceans. Their largest disagreement is the number and level of heating peaks in the tropics. They may produce a single, double, or triple heating peak at a given location. It is argued that cumulus parameterization cannot be the sole source of the disagreement. Implications of such disagreement are discussed.

Assessing the Applicability of the Tropical Convective–Stratiform Paradigm in the Extratropics Using Radar Divergence Profiles

2014 ◽  
Vol 27 (17) ◽  
pp. 6673-6686 ◽  
Author(s):  
Cameron R. Homeyer ◽  
Courtney Schumacher ◽  
Larry J. Hopper
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Horizontal Wind ◽  
Stratiform Rain ◽  
Vertical Divergence ◽  
Upper Level ◽  
The Tropics ◽  
The Impact ◽  
Level Disturbance

Abstract Long-term radar observations from a subtropical location in southeastern Texas are used to examine the impact of storm systems with tropical or extratropical characteristics on the large-scale circulation. Climatological vertical profiles of the horizontal wind divergence are analyzed for four distinct storm classifications: cold frontal (CF), warm frontal (WF), deep convective upper-level disturbance (DC-ULD), and nondeep convective upper-level disturbances (NC-ULD). DC-ULD systems are characterized by weakly baroclinic or equivalent barotropic environments that are more tropical in nature, while the remaining classifications are representative of common midlatitude systems with varying degrees of baroclinicity. DC-ULD systems are shown to have the highest levels of nondivergence (LND) and implied diabatic heating maxima near 6 km, whereas the remaining baroclinic storm classifications have LND altitudes that are about 0.5–1 km lower. Analyses of climatological mean divergence profiles are also separated by rain regions that are primarily convective, stratiform, or indeterminate. Convective–stratiform separations reveal similar divergence characteristics to those observed in the tropics in previous studies, with higher altitudes of implied heating in stratiform rain regions, suggesting that the convective–stratiform paradigm outlined in previous studies is applicable in the midlatitudes. Divergence profiles that cannot be classified as primarily convective or stratiform are typically characterized by large regions of stratiform rain with areas of embedded convection of shallow to moderate extent (i.e., echo tops <10 km). These indeterminate profiles illustrate that, despite not being very deep and accounting for a relatively small fraction of a given storm system, convection dominates the vertical divergence profile and implied heating in these cases.

Convectively Coupled Equatorial Wave Simulations Using the ECMWF IFS and the NOAA GFS Cumulus Convection Schemes in the NOAA GFS Model

2019 ◽  
Vol 147 (11) ◽  
pp. 4005-4025 ◽  
Author(s):  
Lisa Bengtsson ◽  
Juliana Dias ◽  
Maria Gehne ◽  
Peter Bechtold ◽  
Jeffrey Whitaker ◽  
...  
Keyword(s):  
Large Scale ◽  
Cumulus Convection ◽  
Convection Scheme ◽  
Equatorial Wave ◽  
Gfs Model ◽  
Convection Schemes ◽  
Tropical Wave ◽  
Consistent Treatment ◽  
The Tropics ◽  
Moisture Profiles

Abstract There is a longstanding challenge in numerical weather and climate prediction to accurately model tropical wave variability, including convectively coupled equatorial waves (CCEWs) and the Madden–Julian oscillation. For subseasonal prediction, the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) has been shown to be superior to the NOAA Global Forecast System (GFS) in simulating tropical variability, suggesting that the ECMWF model is better at simulating the interaction between cumulus convection and the large-scale tropical circulation. In this study, we experiment with the cumulus convection scheme of the ECMWF IFS in a research version of the GFS to understand which aspects of the IFS cumulus convection scheme outperform those of the GFS convection scheme in the tropics. We show that the IFS cumulus convection scheme produces significantly different tropical moisture and temperature tendency profiles from those simulated by the GFS convection scheme when it is coupled with other physics schemes in the GFS physics package. We show that a consistent treatment of the interaction between parameterized convective plumes in the GFS planetary boundary layer (PBL) and the IFS convection scheme is required for the GFS to replicate the tropical temperature and moisture profiles simulated by the IFS model. The GFS model with the IFS convection scheme, and the consistent treatment between the convection and PBL schemes, produces much more organized convection in the tropics, and generates tropical waves that propagate more coherently than the GFS in its default configuration due to better simulated interaction between low-level convergence and precipitation.

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