scholarly journals NOTES AND CORRESPONDENCE Moistening Processes in the Upper Troposphere by Deep Convection: A Case Study over the Tropical Indian Ocean

2004 ◽  
Vol 82 (3) ◽  
pp. 959-965 ◽  
Author(s):  
E.S CHUNG ◽  
B.J SOHN ◽  
V RAMANATHAN
Keyword(s):  
Indian Ocean ◽  
Deep Convection ◽  
Tropical Indian Ocean ◽  
Upper Troposphere

scholarly journals Convective Characteristics of the Madden–Julian Oscillation over the Central Indian Ocean Observed by Shipborne Radar during DYNAMO

2014 ◽  
Vol 71 (8) ◽  
pp. 2859-2877 ◽  
Author(s):  
Weixin Xu ◽  
Steven A. Rutledge
Keyword(s):  
Time Series ◽  
Indian Ocean ◽  
Phase 1 ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Heavy Precipitation ◽  
Upper Troposphere ◽  
Central Indian Ocean ◽  
Radar Echo ◽  
Two Phases

Abstract This study investigates the convective population and environmental conditions during three MJO events over the central Indian Ocean in late 2011 using measurements collected from the Research Vessel (R/V) Roger Revelle deployed in Dynamics of the MJO (DYNAMO). Radar-based rainfall estimates from the Revelle C-band radar are first placed in the context of larger-scale Tropical Rainfall Measuring Mission (TRMM) rainfall data to demonstrate that the reduced Revelle radar range captured the MJO convective evolution. Time series analysis and MJO phase-based composites of Revelle measurements both support the “recharge–discharge” MJO theory. Time series of echo-top heights indicate that convective deepening during the MJO onset occurs over a 12–16-day period. Composite statistics show evident recharging–discharging features in convection and the environment. Population of shallow/isolated convective cells, SST, CAPE, and the lower-tropospheric moisture increase (recharge) substantially approximately two to three phases prior to the MJO onset. Deep and intense convection and lightning peak in phase 1 when the sea surface temperature and CAPE are near maximum values. However, cells in this phase are not well organized and produce little stratiform rain, possibly owing to reduced shear and a relatively dry upper troposphere. The presence of deep convection leads the mid- to upper-tropospheric humidity by one to two phases, suggesting its role in moistening these levels. During the MJO onset (i.e., phase 2), the mid- to upper troposphere becomes very moist, and precipitation, radar echo-top heights, and the mesoscale extent of precipitation all increase and obtain peak values. Persistent heavy precipitation in these active periods helps reduce the SST and dry/stabilize (or discharge) the atmosphere.

Thermocline warming induced extreme Indian Ocean Dipole in 2019

2021 ◽  
Author(s):  
Yan Du ◽  
Yuhong Zhang ◽  
Lian-Yi Zhang ◽  
Tomoki Tozuka ◽  
Wenju Cai
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Rossby Waves ◽  
Deep Convection ◽  
Tropical Indian Ocean ◽  
Triggering Mechanism ◽  
Bjerknes Feedback ◽  
Easterly Wind ◽  
Positive Indian Ocean Dipole ◽  
The 1960S

<p>The 2019 positive Indian Ocean Dipole (IOD) was the strongest event since the 1960s which developed independently without coinciding El Niño. The dynamics is not fully understood. Here we show that in March-May, westward propagating oceanic Rossby waves, a remnant consequence of the weak 2018 Pacific warm condition, led to anomalous sea surface temperature warming in the southwest tropical Indian Ocean (TIO), inducing deep convection and anomalous easterly winds along the equator, which triggered the initial cooling in the east. In June-August, the easterly wind anomalies continued to evolve through ocean-atmosphere coupling involving Bjerknes feedback and equatorial nonlinear ocean advection, until its maturity in September-November. This study clarifies the contribution of oceanic Rossby waves in the south TIO in different dynamic settings and reveals a new triggering mechanism for extreme IOD events that will help to understand IOD diversity.</p>

Large-Scale Distinctions between MJO and Non-MJO Convective Initiation over the Tropical Indian Ocean

2013 ◽  
Vol 70 (9) ◽  
pp. 2696-2712 ◽  
Author(s):  
Jian Ling ◽  
Chidong Zhang ◽  
Peter Bechtold
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Tropical Indian Ocean ◽  
Negative Temperature ◽  
Maritime Continent ◽  
Zonal Structure ◽  
Convective Initiation ◽  
Upper Troposphere ◽  
The Indian Ocean ◽  
Pressure Surge

Abstract In this study, the authors seek large-scale signals that may distinguish MJO from non-MJO convective events before they start over the Indian Ocean. Three such signals were found. Low-level easterly anomalies extend from the surface to the midtroposphere and move from the western to eastern Indian Ocean. Surface pressure anomalies exhibit a zonal structure of wavenumber 1 with an equatorial low-pressure surge penetrating eastward from Africa through the Indian Ocean and reaching the Maritime Continent. Negative temperature anomalies in the middle to upper troposphere start over the Indian Ocean and move eastward. All of them emerge 20 days before convective initiation of the MJO and move eastward at speeds close to that of the MJO without any direct connection to MJO convection. They are not obviously related to the extratropics in any discernible way or any preceding MJO events. They are absent in non-MJO convective events. These signals provide useful information for forecasting MJO initiation over the Indian Ocean. They can be signatures of a dry dynamics mode of the MJO, if it exists.

Precipitable water over the tropical Indian Ocean derived from NIMBUS 7 satellite data ? A case study

1993 ◽  
Vol 66 (3) ◽  
pp. 325-330
Author(s):  
M. R. Ramesh Kumar ◽  
P. M. Muralidharan ◽  
P. V. Sathe
Keyword(s):  
Indian Ocean ◽  
Satellite Data ◽  
Tropical Indian Ocean ◽  
Precipitable Water

scholarly journals Cloud-scale modelling of the impact of deep convection on the fate of oceanic bromoform in the troposphere: a case study over the west coast of Borneo

2020 ◽  
Author(s):  
Paul D. Hamer ◽  
Virginie Marécal ◽  
Ryan Hossaini ◽  
Michel Pirre ◽  
Gisèle Krysztofiak ◽  
...  
Keyword(s):  
Boundary Layer ◽  
West Coast ◽  
Deep Convection ◽  
Convective System ◽  
The West ◽  
Upper Troposphere ◽  
Convective Systems ◽  
Mixing Ratios ◽  
The Impact

Abstract. Coastal oceans emit bromoform (CHBr3) that can be transported rapidly to the upper troposphere by deep convection. In the troposphere, the spatial and vertical distribution of CHBr3 and its product gases (PGs) depend on emissions, chemical processing, transport by large scale flow, convection, and associated washout. This paper presents a modelling study on the fate of CHBr3 and its PGs in the troposphere. A case study at cloud scale was conducted along the west coast of Borneo, when several deep convective systems triggered in the afternoon and early evening of November 19th 2011. These systems were sampled by the Falcon aircraft during the field campaign of the SHIVA project. We analyse these systems using a simulation with the cloud-resolving meteorological model C-CATT-BRAMS at 2 × 2 km resolution that describes transport, photochemistry, and washout of CHBr3. We find that simulated CHBr3 mixing ratios and the observed values in the boundary layer and the outflow of the convective systems agree. However, the model underestimates the background CHBr3 mixing ratios in the upper troposphere, which suggests a missing source. An analysis of the simulated chemical speciation of bromine within and around each simulated convective system during the mature convective stage reveals that > 85 % of the bromine derived from CHBr3 and its PGs is transported vertically to the point of convective detrainment in the form of CHBr3 and that the remaining small fraction is in the form of organic PGs, principally insoluble brominated carbonyls produced from the photo-oxidation of CHBr3. The model simulates that within the boundary layer and free troposphere, the inorganic PGs are only present in soluble forms, i.e., HBr, HOBr, and BrONO2, and consequently, within the convective clouds, the inorganic PGs are almost entirely removed by wet scavenging. For the conditions of the simulated case study Br2 plays no significant role in the vertical transport of bromine. This likely results from the small simulated quantities of inorganic bromine involved, the presence of HBr in large excess compared to HOBr and the less soluble BrO, and the relatively quick removal of soluble compounds within the convective column. This prevalence of HBr is a result of the wider simulated regional atmospheric composition whereby background tropospheric ozone levels are exceptionally low.

Thermodynamic Response of a High-Resolution Tropical Indian Ocean Model to TOGA COARE Bulk Air–Sea Flux Parameterization: Case Study for the Bay of Bengal (BoB)

2020 ◽  
Vol 177 (8) ◽  
pp. 4025-4044 ◽  
Author(s):  
Subrat Kumar Mallick ◽  
Neeraj Agarwal ◽  
Rashmi Sharma ◽  
K. V. S. R. Prasad ◽  
S. S. V. S. Ramakrishna
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Bay Of Bengal ◽  
Tropical Indian Ocean ◽  
Ocean Model ◽  
Toga Coare ◽  
Flux Parameterization

scholarly journals Discrepancies of Upper Troposphere Summer Thermal Contrast Between Tibetan Plateau and Tropical Indian Ocean in Multiple Data

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoqing Luo ◽  
Jianjun Xu ◽  
Kai Li
Keyword(s):  
Indian Ocean ◽  
Tibetan Plateau ◽  
Linear Trend ◽  
Tropical Indian Ocean ◽  
Reanalysis Data ◽  
Radiosonde Data ◽  
The Tibetan Plateau ◽  
Thermal Contrast ◽  
Upper Troposphere ◽  
Multiple Data

Under the background of global warming, the summer land-sea thermal contrasts at the upper troposphere exists great discrepancies in radiosonde data (IUK, RICH, and RAOBCORE), reanalysis data (JRA-55, NCEP/DOE, and ERA5) and CMIP6 models results (MPI, FGOALS, and CESM2) for the period of 1979-2014. It can be found that the descriptive statistical indicators (i.e., maximum, minimum, and skewness) of the summer land-sea thermal contrasts index (TTI) between the Tibetan Plateau (TP) and the Tropical Indian Ocean (TIO) vary greatly. The ERA5 and JRA-55 data have the best correlation with radiosonde data. The linear trend and running linear trend (RTL) of the radiosonde data are significantly correlated with the reanalysis data, and both show that the land-sea thermal contrast rapidly increasing are in 1990s and the late 2000s, and the period of rapid weakening was early 2000s. This interannual variation may modulated by the decadal signals such as Pacific Decadal Oscillation (PDO). Except for the NCEP/DOE and IUK, other data show that the most significant warming in the TP-TIO region is at the upper troposphere, and the vertical profiles of the summer temperature trend are quite different in different data, and CMIP6 shows an obvious warm bias in the upper troposphere.

scholarly journals The influence of deep convection on HCHO and H<sub>2</sub>O<sub>2</sub> in the upper troposphere over Europe

2017 ◽  
Vol 17 (19) ◽  
pp. 11835-11848 ◽  
Author(s):  
Heiko Bozem ◽  
Andrea Pozzer ◽  
Hartwig Harder ◽  
Monica Martinez ◽  
Jonathan Williams ◽  
...  
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Trace Gases ◽  
Cloud Droplets ◽  
Data Set ◽  
Transport Efficiency ◽  
Upper Troposphere ◽  
Secondary Formation

Abstract. Deep convection is an efficient mechanism for vertical trace gas transport from Earth's surface to the upper troposphere (UT). The convective redistribution of short-lived trace gases emitted at the surface typically results in a C-shaped profile. This redistribution mechanism can impact photochemical processes, e.g. ozone and radical production in the UT on a large scale due to the generally longer lifetimes of species like formaldehyde (HCHO) and hydrogen peroxide (H2O2), which are important HOx precursors (HOx =  OH + HO2 radicals). Due to the solubility of HCHO and H2O2 their transport may be suppressed as they are efficiently removed by wet deposition. Here we present a case study of deep convection over Germany in the summer of 2007 within the framework of the HOOVER II project. Airborne in situ measurements within the in- and outflow regions of an isolated thunderstorm provide a unique data set to study the influence of deep convection on the transport efficiency of soluble and insoluble trace gases. Comparing the in- and outflow indicates an almost undiluted transport of insoluble trace gases from the boundary layer to the UT. The ratios of out : inflow of CO and CH4 are 0.94 ± 0.04 and 0.99 ± 0.01, respectively. For the soluble species HCHO and H2O2 these ratios are 0.55 ± 0.09 and 0.61 ± 0.08, respectively, indicating partial scavenging and washout. Chemical box model simulations show that post-convection secondary formation of HCHO and H2O2 cannot explain their enhancement in the UT. A plausible explanation, in particular for the enhancement of the highly soluble H2O2, is degassing from cloud droplets during freezing, which reduces the retention coefficient.

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