Large differences in the diabatic heat budget of the tropical UTLS in reanalyses

Abstract. We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: MERRA, ERA-Interim, CFSR, JRA-25/JCDAS, and NCEP/NCAR. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Although they may be expected given difficulties in representing moist convection in models, the discrepancies in latent heating are still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention).

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Large differences in reanalyses of diabatic heating in the tropical upper troposphere and lower stratosphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-9565-2013 ◽

2013 ◽

Vol 13 (18) ◽

pp. 9565-9576 ◽

Cited By ~ 63

Author(s):

J. S. Wright ◽

S. Fueglistaler

Keyword(s):

Turbulent Mixing ◽

Lower Stratosphere ◽

Heat Budget ◽

Radiative Heating ◽

Japan Meteorological Agency ◽

Latent Heating ◽

Moist Convection ◽

Climate Data ◽

Upper Troposphere ◽

Tropical Upper Troposphere

Abstract. We present the time mean heat budgets of the tropical upper troposphere (UT) and lower stratosphere (LS) as simulated by five reanalysis models: the Modern-Era Retrospective Analysis for Research and Applications (MERRA), European Reanalysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), Japanese 25-yr Reanalysis and Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS), and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1. The simulated diabatic heat budget in the tropical UTLS differs significantly from model to model, with substantial implications for representations of transport and mixing. Large differences are apparent both in the net heat budget and in all comparable individual components, including latent heating, heating due to radiative transfer, and heating due to parameterised vertical mixing. We describe and discuss the most pronounced differences. Discrepancies in latent heating reflect continuing difficulties in representing moist convection in models. Although these discrepancies may be expected, their magnitude is still disturbing. We pay particular attention to discrepancies in radiative heating (which may be surprising given the strength of observational constraints on temperature and tropospheric water vapour) and discrepancies in heating due to turbulent mixing (which have received comparatively little attention). The largest differences in radiative heating in the tropical UTLS are attributable to differences in cloud radiative heating, but important systematic differences are present even in the absence of clouds. Local maxima in heating and cooling due to parameterised turbulent mixing occur in the vicinity of the tropical tropopause.

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The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-6467-2015 ◽

2015 ◽

Vol 15 (11) ◽

pp. 6467-6486 ◽

Cited By ~ 21

Author(s):

W. Frey ◽

R. Schofield ◽

P. Hoor ◽

D. Kunkel ◽

F. Ravegnani ◽

...

Keyword(s):

Lower Stratosphere ◽

Deep Convection ◽

Horizontal Resolution ◽

Transport Processes ◽

Convective System ◽

Upper Troposphere ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Transport And Mixing ◽

The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection with a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere, but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

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Potential impact of carbonaceous aerosol on the upper troposphere and lower stratosphere (UTLS) and precipitation during Asian summer monsoon in a global model simulation

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-11637-2017 ◽

2017 ◽

Vol 17 (18) ◽

pp. 11637-11654 ◽

Cited By ~ 6

Author(s):

Suvarna Fadnavis ◽

Gayatry Kalita ◽

K. Ravi Kumar ◽

Blaž Gasparini ◽

Jui-Lin Frank Li

Keyword(s):

Lower Stratosphere ◽

Model Simulation ◽

Eastern China ◽

Radiative Heating ◽

Carbonaceous Aerosol ◽

Monsoon Circulation ◽

The Tibetan Plateau ◽

Carbonaceous Aerosols ◽

Gangetic Plain ◽

Upper Troposphere

Abstract. Recent satellite observations show efficient vertical transport of Asian pollutants from the surface to the upper-level anticyclone by deep monsoon convection. In this paper, we examine the transport of carbonaceous aerosols, including black carbon (BC) and organic carbon (OC), into the monsoon anticyclone using of ECHAM6-HAM, a global aerosol climate model. Further, we investigate impacts of enhanced (doubled) carbonaceous aerosol emissions on the upper troposphere and lower stratosphere (UTLS), underneath monsoon circulation and precipitation from sensitivity simulations. The model simulation shows that boundary layer aerosols are transported into the monsoon anticyclone by the strong monsoon convection from the Bay of Bengal, southern slopes of the Himalayas and the South China Sea. Doubling of emissions of both BC and OC aerosols over Southeast Asia (10° S–50° N, 65–155° E) shows that lofted aerosols produce significant warming (0.6–1 K) over the Tibetan Plateau (TP) near 400–200 hPa and instability in the middle/upper troposphere. These aerosols enhance radiative heating rates (0.02–0.03 K day−1) near the tropopause. The enhanced carbonaceous aerosols alter aerosol radiative forcing (RF) at the surface by −4.74 ± 1.42 W m−2, at the top of the atmosphere (TOA) by +0.37 ± 0.26 W m−2 and in the atmosphere by +5.11 ± 0.83 W m−2 over the TP and Indo-Gangetic Plain region (15–35° N, 80–110° E). Atmospheric warming increases vertical velocities and thereby cloud ice in the upper troposphere. Aerosol induced anomalous warming over the TP facilitates the relative strengthening of the monsoon Hadley circulation and increases moisture inflow by strengthening the cross-equatorial monsoon jet. This increases precipitation amounts over India (1–4 mm day−1) and eastern China (0.2–2 mm day−1). These results are significant at the 99 % confidence level.

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Probing the dynamical features of intense pre-monsoon and summer monsoon deep convective systems using ARIES Stratosphere Troposphere Radar (206.5 MHz) over the Central Himalayan region

10.5194/egusphere-egu21-5531 ◽

2021 ◽

Author(s):

Aditya Jaiswal ◽

Manish Naja ◽

Samaresh Bhattacharjee

Keyword(s):

Momentum Flux ◽

General Circulation ◽

Lower Stratosphere ◽

Heat Budget ◽

Monsoon Season ◽

Deep Convection ◽

Himalayan Region ◽

Upper Troposphere ◽

Himalayan Foothills ◽

Dynamical Features

Deep convection is known to be critical for the transport of mass and momentum flux, heat and moisture throughout in the upper troposphere and lower stratosphere region. Hence it modifies the heat budget and general circulation in the atmosphere. Earlier studies have noted very strong instability in the atmosphere over Himalayan foothills, triggering occasional intense convection due to the orographic lifting of the low level moist flow. &#160;However due to the lack of observational network over this complex terrain, a comprehensive analysis of these events and their impacts have not been done.Recently a Stratosphere Troposphere Radar (wind profiler) operating at VHF frequency of 206.5 MHz has been installed at a high altitude site Aryabhatta Research Institute of Observational Sciences (ARIES) (29.4oN, 79.5o E, 1790 m amsl) in Nainital located in Himalayan foothills, a meteorologically sensitive subtropical region. Using the capability of VHF radar of detecting echoes from both clear air and precipitation, &#160;intense deep convection systems were observed on May 5, 2020 and September 2, 2020. Both the events have been studied in details using the temporal and vertical evolution of &#160;radar parameters like total backscattered power and spectral width. Reanalysis data from MERRA-2 and cloud fraction data of IR and Water Vapour channels of INSAT 3D has also been used to investigate underlying synoptic features of the event. Here, it is suggested that deep convection of the pre-monsoon season was induced due to moisture carried by the western disturbance. While the event in monsoon season was due to the easterly moist flow from the Bay of Bengal. The moisture in the mid - troposphere coupled with the orographic lift led to vigorous updrafts and downdrafts of magnitude reaching up to 16 m/s. Updrafts found to be extending well beyond the tropopause into the lower stratosphere region. From the temporal evolution of vertical wind velocity obtained from ST Radar, a clear demarcation between updrafts and downdrafts region was established during the mature phase of the event due to veering of the wind from lower to upper troposphere which also led to the tilting of the updraft cores. During the event the exchange of the vertical flux of horizontal momentum between upper troposphere and lower stratosphere has also been estimated. A significant enhancement (2 &#8211; 3 times) in mean zonal (u'w') and meridional component (v'w') of momentum flux has been observed during convection as compared to quiet period. In the upper troposphere and lower stratosphere region mean flux values even reached up to about 33 m2 s-2. We feel that this study will help in providing the crucial insights of the dynamical features of meso-scale convective phenomenon in the central Himalayan region for the first time.

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Local Balance and Variability of Atmospheric Heat Budget over Oceans: Observation and Reanalysis-Based Estimates

Journal of Climate ◽

10.1175/jcli-d-13-00143.1 ◽

2014 ◽

Vol 27 (2) ◽

pp. 893-913 ◽

Cited By ~ 4

Author(s):

Sun Wong ◽

Tristan S. L’Ecuyer ◽

William S. Olson ◽

Xianan Jiang ◽

Eric J. Fetzer

Keyword(s):

Heat Budget ◽

Deep Convection ◽

Tropical Rainfall Measuring Mission ◽

Heat Fluxes ◽

Radiative Heating ◽

Latent Heating ◽

Heating Rates ◽

Cooling Rates ◽

Atmospheric Heating ◽

Atmospheric Heat

Abstract The authors quantify systematic differences between modern observation- and reanalysis-based estimates of atmospheric heating rates and identify dominant variability modes over tropical oceans. Convergence of heat fluxes between the top of the atmosphere and the surface are calculated over the oceans using satellite-based radiative and sensible heat fluxes and latent heating from precipitation estimates. The convergence is then compared with column-integrated atmospheric heating based on Tropical Rainfall Measuring Mission data as well as the heating calculated using temperatures from the Atmospheric Infrared Sounder and wind fields from the Modern-Era Retrospective Analysis for Research and Applications (MERRA). Corresponding calculations using MERRA and the European Centre for Medium-Range Weather Forecasts Interim Re-Analysis heating rates and heat fluxes are also performed. The geographical patterns of atmospheric heating rates show heating regimes over the intertropical convergence zone and summertime monsoons and cooling regimes over subsidence areas in the subtropical oceans. Compared to observation-based datasets, the reanalyses have larger atmospheric heating rates in heating regimes and smaller cooling rates in cooling regimes. For the averaged heating rates over the oceans in 40°S–40°N, the observation-based datasets have net atmospheric cooling rates (from −15 to −22 W m−2) compared to the reanalyses net warming rates (5.0–5.2 W m−2). This discrepancy implies different pictures of atmospheric heat transport. Wavelet spectra of atmospheric heating rates show distinct maxima of variability in annual, semiannual, and/or intraseasonal time scales. In regimes where deep convection frequently occurs, variability is mainly driven by latent heating. In the subtropical subsidence areas, variability in radiative heating is comparable to that in latent heating.

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How Does Cloud Overlap Affect the Radiative Heating in the Tropical Upper Troposphere/Lower Stratosphere?

Geophysical Research Letters ◽

10.1029/2019gl082602 ◽

2019 ◽

Vol 46 (10) ◽

pp. 5623-5631

Author(s):

Erik Johansson ◽

Abhay Devasthale ◽

Annica M. L. Ekman ◽

Michael Tjernström ◽

Tristan L'Ecuyer

Keyword(s):

Lower Stratosphere ◽

Radiative Heating ◽

Upper Troposphere ◽

Tropical Upper Troposphere

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Observations of Temperature in the Upper Troposphere and Lower Stratosphere of Tropical Weather Disturbances

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-13-0278.1 ◽

2014 ◽

Vol 71 (5) ◽

pp. 1593-1608 ◽

Cited By ~ 12

Author(s):

Christopher A. Davis ◽

David A. Ahijevych ◽

Julie A. Haggerty ◽

Michael J. Mahoney

Keyword(s):

Lower Stratosphere ◽

Deep Convection ◽

Temporal Variations ◽

Radiative Heating ◽

Upper Troposphere ◽

Radial Gradient ◽

Tropospheric Circulation ◽

Tropical Weather ◽

Temperature Profiler ◽

Cold Point

Abstract Microwave temperature profiler (MTP) data are analyzed to document temperature signatures in the upper troposphere and lower stratosphere that accompany Atlantic tropical weather disturbances. The MTP was deployed on the National Science Foundation–National Center for Atmospheric Research Gulfstream V (GV) aircraft during the Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) in August and September 2010. Temporal variations in cold-point temperature compared with infrared cloud-top temperature reveal that organized deep convection penetrated to near or beyond the cold point for each of the four disturbances that developed into a tropical cyclone. Relative to the lower-tropospheric circulation center, MTP and dropsonde data confirmed a stronger negative radial gradient of temperature in the upper troposphere (10–13 km) of developing disturbances prior to genesis compared with nondeveloping disturbances. The MTP data revealed a somewhat higher and shallower area of relative warmth near the center when compared with dropsonde data. MTP profiles through anvil cloud depicted cooling near 15 km and warming in the lower stratosphere near the time of maximum coverage of anvil clouds shortly after sunrise. Warming occurred through a deep layer of the upper troposphere toward local noon, presumably associated with radiative heating in cloud. The temperature signatures of anvil cloud above 10-km altitude contributed to the radial gradient of temperature because of the clustering of deep convection near the center of circulation. However, it is concluded that these signatures may be more a result of properties of convection than a direct distinguishing factor of genesis.

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The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-1041-2015 ◽

2015 ◽

Vol 15 (1) ◽

pp. 1041-1091 ◽

Cited By ~ 1

Author(s):

W. Frey ◽

R. Schofield ◽

P. Hoor ◽

D. Kunkel ◽

F. Ravegnani ◽

...

Keyword(s):

Lower Stratosphere ◽

Deep Convection ◽

Horizontal Resolution ◽

Transport Processes ◽

Convective System ◽

Upper Troposphere ◽

Tropical Tropopause Layer ◽

Tropical Tropopause ◽

Transport And Mixing ◽

The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection to a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

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Overshooting of clean tropospheric air in the tropical lower stratosphere as seen by the CALIPSO lidar

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-9683-2011 ◽

2011 ◽

Vol 11 (18) ◽

pp. 9683-9696 ◽

Cited By ~ 32

Author(s):

J.-P. Vernier ◽

J.-P. Pommereau ◽

L. W. Thomason ◽

J. Pelon ◽

A. Garnier ◽

...

Keyword(s):

Biomass Burning ◽

Lower Stratosphere ◽

Thermal Structure ◽

Radiative Heating ◽

Major Contributor ◽

Upper Troposphere ◽

Tropical Tropopause Layer ◽

Volcanic Plumes ◽

Tropical Tropopause ◽

Organic Particles

Abstract. The evolution of aerosols in the tropical upper troposphere/lower stratosphere between June 2006 and October 2009 is examined using the observations of the space borne CALIOP lidar aboard the CALIPSO satellite. Superimposed on several volcanic plumes and soot from an extreme biomass-burning event in 2009, the measurements reveal the existence of fast-cleansing episodes in the lower stratosphere to altitudes as high as 20 km. The cleansing of the layer, which extends from 14 to 20 km, takes place within 1 to 4 months during the southern tropics convective season that transports aerosol-poor tropospheric air into the lower stratosphere. In contrast, the convective season of the Northern Hemisphere summer shows an increase in the particle load at the tropopause consistent with a lofting of air rich with aerosols. These aerosols can consist of surface-derived material such as mineral dust and soot as well as liquid sulfate and organic particles. The flux of tropospheric air during the Southern Hemisphere convective season derived from CALIOP observations is shown to be 5 times at 16 km and 20 times at 19 km larger, respectively, than that associated with flux caused by slow ascent through radiative heating. These results suggest that convective overshooting is a major contributor to troposphere-to-stratosphere transport with concomitant implications for the Tropical Tropopause Layer top height, the humidity, the photochemistry and the thermal structure of the layer.

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Representation of tropical deep convection in atmospheric models – Part 1: Meteorology and comparison with satellite observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-2765-2011 ◽

2011 ◽

Vol 11 (6) ◽

pp. 2765-2786 ◽

Cited By ~ 26

Author(s):

M. R. Russo ◽

V. Marécal ◽

C. R. Hoyle ◽

J. Arteta ◽

C. Chemel ◽

...

Keyword(s):

Water Vapour ◽

Seasonal Cycle ◽

Lower Stratosphere ◽

Weather Prediction ◽

Tropical Convection ◽

Satellite Observations ◽

Radiative Heating ◽

Atmospheric Models ◽

Upper Troposphere ◽

The Tropics

Abstract. Fast convective transport in the tropics can efficiently redistribute water vapour and pollutants up to the upper troposphere. In this study we compare tropical convection characteristics for the year 2005 in a range of atmospheric models, including numerical weather prediction (NWP) models, chemistry transport models (CTMs), and chemistry-climate models (CCMs). The model runs have been performed within the framework of the SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) project. The characteristics of tropical convection, such as seasonal cycle, land/sea contrast and vertical extent, are analysed using satellite observations as a benchmark for model simulations. The observational datasets used in this work comprise precipitation rates, outgoing longwave radiation, cloud-top pressure, and water vapour from a number of independent sources, including ERA-Interim analyses. Most models are generally able to reproduce the seasonal cycle and strength of precipitation for continental regions but show larger discrepancies with observations for the Maritime Continent region. The frequency distribution of high clouds from models and observations is calculated using highly temporally-resolved (up to 3-hourly) cloud top data. The percentage of clouds above 15 km varies significantly between the models. Vertical profiles of water vapour in the upper troposphere-lower stratosphere (UTLS) show large differences between the models which can only be partly attributed to temperature differences. If a convective plume reaches above the level of zero net radiative heating, which is estimated to be ~15 km in the tropics, the air detrained from it can be transported upwards by radiative heating into the lower stratosphere. In this context, we discuss the role of tropical convection as a precursor for the transport of short-lived species into the lower stratosphere.

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