An Evaluation of the Proposed Mechanism of the Adaptive Infrared Iris Hypothesis Using TRMM VIRS and PR Measurements

2005 ◽  
Vol 18 (20) ◽  
pp. 4185-4194 ◽  
Author(s):  
Anita D. Rapp ◽  
Christian Kummerow ◽  
Wesley Berg ◽  
Brian Griffith
Keyword(s):  
Surface Temperature ◽  
Deep Convection ◽  
Cloud Amount ◽  
Tropical Rainfall Measuring Mission ◽  
Convective Cloud ◽  
Sea Surface ◽  
Central Pacific ◽  
Convective Clouds ◽  
Brightness Temperatures ◽  
Surface Rainfall

Abstract Significant controversy surrounds the adaptive infrared iris hypothesis put forth by Lindzen et al., whereby tropical anvil cirrus detrainment is hypothesized to decrease with increasing sea surface temperature (SST). This dependence would act as an iris, allowing more infrared radiation to escape into space and inhibiting changes in the surface temperature. This hypothesis assumes that increased precipitation efficiency in regions of higher sea surface temperatures will reduce cirrus detrainment. Tropical Rainfall Measuring Mission (TRMM) satellite measurements are used here to investigate the adaptive infrared iris hypothesis. Pixel-level Visible and Infrared Scanner (VIRS) 10.8-μm brightness temperature data and precipitation radar (PR) rain-rate data from TRMM are collocated and matched to determine individual convective cloud boundaries. Each cloudy pixel is then matched to the underlying SST. This study examines single- and multicore convective clouds separately to directly determine if a relationship exists between the size of convective clouds, their precipitation, and the underlying SSTs. In doing so, this study addresses some of the criticisms of the Lindzen et al. study by eliminating their more controversial method of relating bulk changes of cloud amount and SST across a large domain in the Tropics. The current analysis does not show any significant SST dependence of the ratio of cloud area to surface rainfall for deep convection in the tropical western and central Pacific. Results do, however, suggest that SST plays an important role in the ratio of cloud area and surface rainfall for warm rain processes. For clouds with brightness temperatures between 270 and 280 K, a net decrease in cloud area normalized by rainfall of 5% per degree SST was found.

scholarly journals Extreme Convection and Tropical Climate Variability: Scaling of Cold Brightness Temperatures to Sea Surface Temperature

2016 ◽  
Vol 29 (10) ◽  
pp. 3893-3905 ◽  
Author(s):  
Sun Wong ◽  
João Teixeira
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Southern Oscillation ◽  
Convective Cloud ◽  
Sea Surface ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Test Bed ◽  
Brightness Temperatures ◽  
Warming World

Abstract Changes in tropical convective events provide a test bed for understanding changes of extreme convection in a warming climate. Because convective cloud top in deep convection is associated with cold brightness temperatures (BTs) in infrared window channels, variability in global convective events can be studied by spaceborne measurements of BTs. The sensitivity of BTs, directly measured by an Atmospheric Infrared Sounder (AIRS) window channel, to natural changes (the seasonal cycle and El Niño–Southern Oscillation) in tropical sea surface temperature (SST) is examined. It is found that tropical average BTs (over the ocean) at the low percentiles of their probability distributions scale with tropical average SSTs (higher SST leading to colder BTs), with the lower percentiles being significantly more sensitive to changes in SST. The sensitivity is reduced for high percentiles of BT and is insignificant for the median BT, and has similar magnitudes for the two natural changes used in the study. The regions where the lower-percentile BTs are most sensitive to SST are near the edges of the convection active areas (intertropical convergence zone and South Pacific convergence zone), including areas with active tropical cyclone activity. Since cold BTs of lower percentiles represent stronger convective events, this study provides, for the first time, global observational evidence of higher sensitivity of changes in stronger convective activity to a changing SST. This result has important potential implications in answering the key climate question of how severe tropical convection will change in a warming world.

scholarly journals Subseasonal Forecasts of the Northern Queensland Floods of February 2019: Causes and Forecast Evaluation

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 758
Author(s):  
Wayne Yuan-Huai Tsai ◽  
Mong-Ming Lu ◽  
Chung-Hsiung Sui ◽  
Yin-Min Cho
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Austral Summer ◽  
Rainfall Event ◽  
Monsoon Depression ◽  
Forecast Skill ◽  
Sea Surface ◽  
Central Pacific ◽  
Percentile Rank ◽  
Extended Range

During the austral summer 2018/19, devastating floods occurred over northeast Australia that killed approximately 625,000 head of cattle and inundated over 3000 homes in Townsville. In this paper, the disastrous event was identified as a record-breaking subseasonal peak rainfall event (SPRE). The SPRE was mainly induced by an anomalously strong monsoon depression that was modulated by the convective phases of an MJO and an equatorial Rossby (ER) wave. The ER wave originated from an active equatorial deep convection associated with the El Niño warm sea surface temperatures near the dateline over the central Pacific. Based on the S2S Project Database, we analyzed the extended-range forecast skill of the SPRE from two different perspectives, the monsoon depression represented by an 850-hPa wind shear index and the 15-day accumulated precipitation characterized by the percentile rank (PR) and the ratio to the three-month seasonal (DJF) totals. The results of four S2S models of this study suggest that the monsoon depression can maintain the same level of skill as the short-range (3 days) forecast up to 8–10 days. For precipitation parameters, the conclusions are similar to the monsoon depression. For the 2019 northern Queensland SPRE, the model forecast was, in general, worse than the expectation derived from the hindcast analysis. The clear modulation of the ER wave that enhanced the SPRE monsoon depression circulation and precipitation is suspected as the main cause for the lower forecast skill. The analysis procedure proposed in this study can be applied to analyze the SPREs and their associated large-scale drivers in other regions.

scholarly journals Self‐Aggregation of Convective Clouds With Interactive Sea Surface Temperature

2020 ◽  
Vol 12 (11) ◽  
Author(s):  
S. Shamekh ◽  
C. Muller ◽  
J.‐P. Duvel ◽  
F. D'Andrea
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Convective Clouds ◽  
Self Aggregation

Validation of the AATSR Meteo Product Sea Surface Temperature

2006 ◽  
Vol 23 (5) ◽  
pp. 711-726 ◽  
Author(s):  
A. G. O'Carroll ◽  
J. G. Watts ◽  
L. A. Horrocks ◽  
R. W. Saunders ◽  
N. A. Rayner
Keyword(s):  
Standard Deviation ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
European Space Agency ◽  
Tropical Rainfall Measuring Mission ◽  
Daily Basis ◽  
Mean Difference ◽  
Sea Surface ◽  
Lower Latitude

Abstract The Advanced Along Track Scanning Radiometer (AATSR) Sea Surface Temperature (SST) Meteo product, a fast-delivery level-2 product at 10 arc min spatial resolution, has been available from the European Space Agency (ESA) since 19 August 2002. Validation has been performed on these data at the Met Office on a daily basis, with a 2-day lag from data receipt. Meteo product skin SSTs have been compared with point measurements of buoy SST, a 1° climate SST analysis field compiled from in situ measurements and Advanced Very High Resolution Radiometer (AVHRR) SSTs, and a 5° latitude–longitude 5-day averaged in situ dataset. Comparisons of the AATSR Meteo product against Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) SSTs are also presented. These validation results have confirmed the AATSR Meteo product skin SST to be within ±0.3 K of in situ data. Comparisons of the AATSR skin SSTs against buoy SSTs, from 19 August 2002 to 20 August 2003, give a mean difference (AATSR – buoy) of 0.04 K (standard deviation = 0.28 K) during nighttime, and a mean difference of 0.02 K (standard deviation = 0.39 K) during the day. Analyses of the buoy matchups have shown that there is no cool skin effect observed in the nighttime observations, implying that the three-channel AATSR product skin SST may be 0.1–0.2 K too warm. Comparisons with TMI SSTs confirm that the lower-latitude SSTs are not significantly affected by residual cloud contamination.

scholarly journals Multiyear CloudSat and CALIPSO Observations of the Dependence of Cloud Vertical Distribution on Sea Surface Temperature and Tropospheric Dynamics

2014 ◽  
Vol 27 (2) ◽  
pp. 672-683 ◽  
Author(s):  
Anish Kumar M. Nair ◽  
K. Rajeev
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Spatial Gradient ◽  
Frequency Of Occurrence ◽  
Altitude Distribution ◽  
Convective Clouds ◽  
Dynamical Parameters ◽  
Vertical Development

Abstract Utilizing the synergy of the capabilities of CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and ~4.5 years of their observations, this paper investigates the dependence of the altitude distribution and thickness of tropical clouds on sea surface temperature (SST). Variations in the altitude distribution of clouds with SST show three distinct regimes: SST < 27.5°C, 27.5° < SST < 29°C, and SST > 29°C. At an SST < 27.5°C, the convection is rather weak, so that most of the clouds are limited to <2-km altitude with peak occurrence at 1–1.5 km. The frequency of occurrence of the low-altitude clouds as well as the prominence of the peak at ~1.5 km consistently decreases for SST > 24°C. Vertical development of clouds through the 3–12-km-altitude region increases for SST > 27.5°C to achieve maximum cloud occurrence and thickness in the SST range of 29°–30.5°C. Penetration of the deep convective clouds to altitudes >15 km and their frequency of occurrence increase with SST until ~30°C. These observations reveal two differences with the SST dependence of total cloudiness observed using passive imager data: (i) the increase in cloudiness at an SST > 26°–27°C observed using the imager data is found to be influenced by the increase in cirrus clouds generated by deep convective outflows and is not directly driven by the local SST, and (ii) the total cloudiness does not decrease for SST > 29.5°C as observed using imagers, but weakly increases until an SST of ~30.5°C. The role of the spatial gradient of SST and atmospheric dynamical parameters in modulating the observed SST dependence of cloudiness at different SST regimes is investigated.

scholarly journals Predicting East African spring droughts using Pacific and Indian Ocean sea surface temperature indices

2014 ◽  
Vol 11 (3) ◽  
pp. 3111-3136 ◽  
Author(s):  
C. Funk ◽  
A. Hoell ◽  
S. Shukla ◽  
I. Bladé ◽  
B. Liebmann ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Rainfall Variability ◽  
Sea Surface ◽  
Southern Ethiopia ◽  
East African ◽  
Central Pacific ◽  
Boreal Spring ◽  
Central Indian Ocean

Abstract. In southern Ethiopia, Eastern Kenya, and southern Somalia, poor boreal spring rains in 1999, 2000, 2004, 2007, 2008, 2009, and 2011 contributed to severe food insecurity and high levels of malnutrition. Predicting rainfall deficits in this region on seasonal and decadal time frames can help decision makers implement disaster risk reduction measures while guiding climate-smart adaptation and agricultural development. Building on recent research that links more frequent droughts in that region to a stronger Walker Circulation, warming in the Indo-Pacific warm pool, and an increased western Pacific sea surface temperature (SST) gradient, we show that the two dominant modes of East African boreal spring rainfall variability are tied, respectively, to western-central Pacific and central Indian Ocean SST. Variations in these rainfall modes can be predicted using two previously defined SST indices – the West Pacific Gradient (WPG) and Central Indian Ocean index (CIO), with the WPG and CIO being used, respectively, to predict the first and second rainfall modes. These simple indices can be used in concert with more sophisticated coupled modeling systems and land surface data assimilations to help inform early warning and guide climate outlooks.

scholarly journals Variability of vertical structure of precipitation with sea surface temperature over the Arabian Sea and the Bay of Bengal as inferred by TRMM PR measurements

2018 ◽  
Author(s):  
Kadiri Saikranthi ◽  
Basivi Radhakrishna ◽  
Thota Narayana Rao ◽  
Sreedharan Krishnakumari Satheesh
Keyword(s):  
Water Vapor ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Vertical Structure ◽  
Tropical Rainfall Measuring Mission ◽  
Sea Surface ◽  
Cloud Formation ◽  
Freezing Level

Abstract. Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) 2A25 reflectivity profiles data during the period 1998–2013 are used to study the differences in the vertical structure of precipitation and its variation with sea surface temperature (SST) over the Arabian Sea (AS) and the Bay of Bengal (BOB). Even though the AS and the BOB are parts of the Indian Ocean, they exhibit distinct features in vertical structure of precipitation and its variation with SST. The variation of reflectivity and precipitation echo top occurrence with SST is remarkable over the AS but trivial over the BOB. The median reflectivity increases with SST at all heights below 10 km altitude, but the increase is prominent below the freezing level height over the AS. On the other hand, irrespective of altitude, reflectivity profiles are same at all SSTs over the BOB. To understand these differences, variation of aerosols, cloud and water vapor with SST is studied over these seas. At SSTs less than 27 °C, the observed high aerosol optical depth (AOD) and low total column water vapor (TCWV) over the AS results in small Cloud effective radius (CER) values and low reflectivity. As SST increases AOD decreases and TCWV increases, which result in large CER and high reflectivity. Over the BOB the change in AOD, TCWV and CER with SST is marginal. Thus, the observed variations in reflectivity profiles seem to be present from the cloud formation stage itself over both the seas.

scholarly journals Effects of Salinity Variability on Recent El Niño Events

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 475 ◽  
Author(s):  
Hai Zhi ◽  
Rong-Hua Zhang ◽  
Pengfei Lin ◽  
Shiwei Shi
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Surface Salinity ◽  
Central Pacific ◽  
Salinity Variability ◽  
Central Equatorial Pacific

Ocean salinity variability provides a new way to study the evolution of the the El Niño-Southern Oscillation (ENSO). Comparisons between the salinity variation and related processes responsible for sea surface temperature anomaly (SSTA) were extensively examined for the two strong El Niño (EN) events in 1997/1998 and 2015/2016, and a special EN event in 2014/2015. The results show that the development of EN is significantly correlated with a sea surface salinity anomaly (SSSA) in the tropical western-central Pacific. In the spring of 1997 and 2015 with strong EN events, the western-central equatorial Pacific exhibited significant negative SSSA that propagated eastward to the west of the dateline. The negative SSSA induced increased barrier layer thickness (BLT) which enhanced sea surface temperature (SST) warming in the tropical central Pacific. In contrast, although a negative SSSA occurred during April of the 2014/2015 weak EN event in the western-central equatorial Pacific, this SSSA was mainly confined to between 160° E and 180° E without significant eastward movement, resulting in a weakened BLT thickening process and a weak modulation effect on SST. We also confirm that the surface forcing associated with fresh water flux (FWF: evaporation (E) minus precipitation (P)) plays a prominent role in the surface salinity tendency in the tropical Pacific during EN events. Moreover, the negative FWF anomaly leads a strong negative SSSA by two months. Compared with the two strong ENs, the early negative FWF anomaly in the weak 2014/2015 EN did not present distinct development and eastward propagation and weakened rapidly in the summer of 2015. We demonstrate that change in salinity can modulate the ENSO, and the variation of SSSA and associated physical processes in the tropical western-central Pacific and could be used as an indicator for predicting the development of ENSO.

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