scholarly journals Are elevated moist layers a blind spot for hyperspectral infrared sounders? A model study

2021 ◽  
Vol 14 (11) ◽  
pp. 7025-7044
Author(s):  
Marc Prange ◽  
Manfred Brath ◽  
Stefan A. Buehler
Keyword(s):  
Heating Rate ◽  
Local Heating ◽  
Optimal Estimation ◽  
Forecast Model ◽  
Temperature Inversion ◽  
Radiative Heating ◽  
Reference Dataset ◽  
Tropical Ocean ◽  
Systematic Analysis ◽  
New Framework

Abstract. The ability of the hyperspectral satellite-based passive infrared (IR) instrument IASI to resolve elevated moist layers (EMLs) within the free troposphere is investigated. EMLs are strong moisture anomalies with significant impact on the radiative heating rate profile and typically coupled to freezing level detrainment from convective cells in the tropics. A previous case study by Stevens et al. (2017) indicated inherent deficiencies of passive satellite-based remote sensing instruments in resolving an EML. In this work, we first put the findings of Stevens et al. (2017) into the context of other retrieval case studies of EML-like structures, showing that such structures can in principle be retrieved, but retrievability depends on the retrieval method and the exact retrieval setup. To approach a first more systematic analysis of EML retrievability, we introduce our own basic optimal estimation (OEM) retrieval, which for the purpose of this study is based on forward-modelled (synthetic) clear-sky observations. By applying the OEM retrieval to the same EML case as Stevens et al. (2017), we find that a lack of independent temperature information can significantly deteriorate the humidity retrieval due to a strong temperature inversion at the EML top. However, we show that by employing a wider spectral range of the hyperspectral IR observation, this issue can be avoided and EMLs can generally be resolved. We introduce a new framework for the identification and characterization of moisture anomalies, a subset of which are EMLs, to specifically quantify the retrieval's ability to capture moisture anomalies. The new framework is applied to 1288 synthetic retrievals of tropical ocean short-range forecast model atmospheres, allowing for a direct statistical comparison of moisture anomalies between the retrieval and the reference dataset. With our basic OEM retrieval, we find that retrieved moisture anomalies are on average 17 % weaker and 15 % thicker than their true counterparts. We attribute this to the retrieval smoothing error and the fact that rather weak and narrow moisture anomalies are most frequently missed by the retrieval. Smoothing is found to also constrain the magnitude of local heating rate extremes associated with moisture anomalies, particularly for the strongest anomalies that are found in the lower to mid troposphere. In total, about 80 % of moisture anomalies in the reference dataset are found by the retrieval. Below 5 km altitude, this fraction is only of the order of 52 %. We conclude that the retrieval of lower- to mid-tropospheric moisture anomalies, in particular of EMLs, is possible when the anomaly is sufficiently strong and its thickness is at least of the order of about 1.5 km. This study sets the methodological basis for more comprehensively investigating EMLs based on real hyperspectral IR observations and their operational products in the future.

scholarly journals Light absorption by marine cyanobacteria affects tropical climate mean state and variability

2018 ◽  
Vol 9 (4) ◽  
pp. 1283-1300 ◽  
Author(s):  
Hanna Paulsen ◽  
Tatiana Ilyina ◽  
Johann H. Jungclaus ◽  
Katharina D. Six ◽  
Irene Stemmler
Keyword(s):  
Light Absorption ◽  
Large Scale ◽  
Local Heating ◽  
Light Attenuation ◽  
Tropical Climate ◽  
Climate System ◽  
Radiative Heating ◽  
Subsurface Water ◽  
Marine Cyanobacteria ◽  
Tropical Ocean

Abstract. Observations indicate that positively buoyant marine cyanobacteria, which are abundant throughout the tropical and subtropical ocean, have a strong local heating effect due to light absorption at the ocean surface. How these local changes in radiative heating affect the climate system on the large scale is unclear. We use the Max Planck Institute Earth System Model (MPI-ESM), include light absorption by cyanobacteria, and find a considerable cooling effect on tropical sea surface temperature (SST) in the order of 0.5 K on a climatological timescale. This cooling is caused by local shading of subtropical subsurface water by cyanobacteria that is upwelled at the Equator and in eastern boundary upwelling systems. Implications for the climate system include a westward shift of the Walker circulation and a weakening of the Hadley circulation. The amplitude of the seasonal cycle of SST is increased in large parts of the tropical ocean by up to 25 %, and the tropical Pacific interannual variability is enhanced by approx. 20 %. This study emphasizes the sensitivity of the tropical climate system to light absorption by cyanobacteria due to its regulative effect on tropical SST. Generally, including phytoplankton-dependent light attenuation instead of a globally uniform attenuation depth improves some of the major model temperature biases, indicating the relevance of taking this biophysical feedback into account in climate models.

scholarly journals Light absorption by marine cyanobacteria affects tropical climate mean state and variability

2018 ◽  
Author(s):  
Hanna Paulsen ◽  
Tatiana Ilyina ◽  
Johann H. Jungclaus ◽  
Katharina D. Six ◽  
Irene Stemmler
Keyword(s):  
Light Absorption ◽  
Local Heating ◽  
Light Attenuation ◽  
Tropical Climate ◽  
Climate System ◽  
Radiative Heating ◽  
Subsurface Water ◽  
Marine Cyanobacteria ◽  
Heating Effect ◽  
Tropical Ocean

Abstract. Observations indicate that positively buoyant marine cyanobacteria, which are abundant throughout the tropical and subtropical ocean, have a strong local heating effect due to light absorption at the ocean surface. How these local changes in radiative heating affect the climate system on the large scale is unclear as of yet. We use the Max Planck Institute Earth System Model (MPI-ESM) and find that – in contrast to the heating effect which was reported in previous studies – cyanobacteria have a considerable cooling effect on tropical climatological sea surface temperature (SST) in the order of 0.5 K. This cooling is caused by local shading of subtropical subsurface water that is upwelled at the equator and in eastern boundary upwelling systems. Implications for the climate system include an expansion of the Hadley cells and a westward shift of the Walker circulation. The amplitude of the seasonal cycle of SST is increased in large parts of the tropical ocean by up to 25 %, and the tropical Pacific interannual variability is enhanced by ∼ 20 %. This study emphasizes the sensitivity of the tropical climate system to light absorption by the specific phytoplankton group of cyanobacteria due to its regulative effect on tropical SST. Generally, including the phytoplankton-dependent light attenuation instead of a globally uniform attenuation depth improves some of the major model temperature biases, indicating the relevance of taking into account this bio-physical feedback in climate models.

Maintenance of Lower Tropospheric Temperature Inversion in the Saharan Air Layer by Dust and Dry Anomaly

2009 ◽  
Vol 22 (19) ◽  
pp. 5149-5162 ◽  
Author(s):  
Sun Wong ◽  
Andrew E. Dessler ◽  
Natalie M. Mahowald ◽  
Ping Yang ◽  
Qian Feng
Keyword(s):  
Water Vapor ◽  
Radiative Transfer ◽  
Heating Rate ◽  
Temperature Inversion ◽  
Dust Content ◽  
Radiative Heating ◽  
Specific Humidity ◽  
Transfer Model ◽  
Tropospheric Temperature ◽  
Saharan Air Layer

Abstract The role of Saharan dust and dry anomaly in maintaining the temperature inversion in the Saharan air layer (SAL) is investigated. The dust aerosol optical thickness (AOT) in the SAL is inferred from the measurements taken by Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), and the corresponding temperature and specific humidity anomalies are identified using the National Centers for Environmental Prediction (NCEP) data in August–September over the North Atlantic tropical cyclone (TC) main development region (MDR; 10°–20°N, 40°–60°W). The authors also study the SAL simulated in the National Center of Atmospheric Research (NCAR) Community Atmosphere Model, version 3 (CAM3), coupled with dust radiative effect. It is found that higher AOT is associated with warmer and dryer anomalies below 700 hPa, which increases the atmospheric stability. The calculated instantaneous radiative heating anomalies from a radiative transfer model indicate that both the dust and low humidity are essential to maintaining the temperature structure in the SAL against thermal relaxation. At 850 hPa, heating anomalies caused by both the dust and dry anomalies (for AOT > 0.8) are 0.2–0.4 K day−1. The dust heats the atmosphere below 600 hPa, while the dry anomaly cools the atmosphere below 925 hPa, resulting in a peak of heating rate anomaly located at 700–850 hPa. In the eastern Atlantic, dust contributes about 50% of the heating rate anomaly. Westward of 40°W, when the dust content becomes small (AOT < 0.6), the heating rates are more sensitive to the water vapor profile used in the radiative transfer calculation. Retrieving or simulating correct water vapor profiles is essential to the assessment of the SAL heating budgets in regions where the dust content in the SAL is small.

A global record of single-layered ice cloud properties and associated radiative heating rate profiles from an A-Train perspective

2019 ◽  
Vol 53 (5-6) ◽  
pp. 3069-3088 ◽  
Author(s):  
Erica K. Dolinar ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Jonathan H. Jiang ◽  
Norman G. Loeb ◽  
...  
Keyword(s):  
Heating Rate ◽  
Radiative Heating ◽  
Ice Cloud ◽  
Cloud Properties

scholarly journals Quantifying the mass loading of particles in an ash cloud remobilized from tephra deposits on Iceland

2017 ◽  
Vol 17 (7) ◽  
pp. 4401-4418 ◽  
Author(s):  
Frances Beckett ◽  
Arve Kylling ◽  
Guðmunda Sigurðardóttir ◽  
Sibylle von Löwis ◽  
Claire Witham
Keyword(s):  
Infrared Imaging ◽  
North Atlantic Ocean ◽  
Dispersion Model ◽  
Source Area ◽  
Optimal Estimation ◽  
Temperature Inversion ◽  
Dispersion Modelling ◽  
Satellite Measurements ◽  
Tephra Deposits ◽  
Ash Cloud

Abstract. On 16–17 September 2013 strong surface winds over tephra deposits in southern Iceland led to the resuspension and subsequent advection of significant quantities of volcanic ash. The resulting resuspended ash cloud was transported to the south-east over the North Atlantic Ocean and, due to clear skies at the time, was exceptionally well observed in satellite imagery. We use satellite-based measurements in combination with radiative transfer and dispersion modelling to quantify the total mass of ash resuspended during this event. Typically ash clouds from explosive eruptions are identified in satellite measurements from a negative brightness temperature difference (BTD) signal; however this technique assumes that the ash resides at high levels in the atmosphere. Due to a temperature inversion in the troposphere over southern Iceland during 16 September 2013, the resuspended ash cloud was constrained to altitudes of  <  2 km a.s.l. We show that a positive BTD signal can instead be used to identify ash-containing pixels from satellite measurements. The timing and location of the ash cloud identified using this technique from measurements made by the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (NPP) satellite agree well with model predictions using the dispersion model NAME (Numerical Atmospheric-dispersion Modelling Environment). Total column mass loadings are determined from the VIIRS data using an optimal estimation technique which accounts for the low altitude of the resuspended ash cloud and are used to calibrate the emission rate in the resuspended ash scheme in NAME. Considering the tephra deposits from the recent eruptions of Eyjafjallajökull and Grímsvötn as the potential source area for resuspension for this event, we estimate that  ∼  0.2 Tg of ash was remobilized during 16–17 September 2013.

scholarly journals Do direct-access and indirect-access adaptation projects differ in their focus on local communities? A systematic analysis of 63 Adaptation Fund projects

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Ornsaran Pomme Manuamorn ◽  
Robbert Biesbroek
Keyword(s):  
Recent Literature ◽  
Local Communities ◽  
Comparative Assessment ◽  
Direct Access ◽  
Policy Adoption ◽  
Assessment Framework ◽  
Systematic Analysis ◽  
Adaptation Investment ◽  
New Framework

AbstractRecent literature suggests that direct national access to multilateral climate funds could promote climate change adaptation investment that focuses more on the needs of vulnerable local communities when compared to indirect access through multilateral agencies. However, there has been no systematic comparative assessment of the level of community focus of direct-access and indirect-access projects. The lack of a standardized methodology to assess the level of community-focused adaptation has also constrained such comparison. To address this gap, this paper proposes a new framework to assess the level of community focus in adaptation projects, using a combination of financial, participatory, devolutionary, and design for policy adoption and replicability criteria. Using the Adaptation Fund (AF) as a case study, we apply the framework to systematically assess 63 projects approved by the Fund as of May 2017, comprising 22 direct-access and 41 indirect-access projects. We find that direct-access projects are more community-focused than indirect-access projects because they exhibit higher community-oriented financial, participatory, and devolutionary characteristics. We find no difference between the direct-access and indirect-access projects with regard to how they are designed to promote policy adoption and replicability of AF project-financed adaptation actions through policy and geographical mainstreaming. Our findings contribute to an improved understanding of the pattern of adaptation investment that takes place in developing countries with the support of international adaptation finance under both access modalities. The proposed assessment framework could also inform the development of a standardized methodology to track the delivery of international adaptation finance to the community level.

scholarly journals Radiative Heating Rate Profiles over the Southeast Atlantic Ocean during the 2016 and 2017 Biomass Burning Seasons

2020 ◽  
Author(s):  
Allison B. Marquardt Collow ◽  
Mark A. Miller ◽  
Lynne C. Trabachino ◽  
Michael P. Jensen ◽  
Meng Wang
Keyword(s):  
Atlantic Ocean ◽  
Heating Rate ◽  
Biomass Burning ◽  
Radiative Heating ◽  
Aerosol Layer ◽  
Field Campaign ◽  
Cloud Structure ◽  
Ascension Island ◽  
Biomass Burning Aerosol ◽  
Aerosol Plume

Abstract. Marine boundary layer clouds, including the transition from stratocumulus to cumulus, are poorly represented in numerical weather prediction and general circulation models. Further uncertainties in the cloud structure arise in the presence of biomass burning carbonaceous aerosol, as is the case over the southeast Atlantic Ocean where biomass burning aerosol is transported from the African continent. As the aerosol plume progresses across the southeast Atlantic Ocean, radiative heating within the aerosol layer has the potential to alter the thermodynamic environment and therefore the cloud structure; however, this has yet to be quantified. The deployment of the First Atmospheric Radiation Measurement Mobile Facility (AMF1) in support of the Layered Atlantic Smoke Interactions with Clouds (LASIC) field campaign provided a unique opportunity to collect observations of cloud and aerosol properties during two consecutive biomass burning seasons during July through October of 2016 and 2017 over Ascension Island (7.96 S, 14.35 W). Using observed profiles of temperature, humidity, and clouds from the LASIC field campaign, alongside aerosol optical properties from the Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) as input for the Rapid Radiation Transfer Model (RRTM), profiles of the radiative heating rate due to aerosols and clouds were computed. Radiative heating is also assessed across the southeast Atlantic Ocean using an ensemble of back trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Idealized experiments using RRTM with and without aerosols and a range of values for the single scattering albedo demonstrate that shortwave (SW) heating within the aerosol layer above Ascension Island can locally range between 2 and 8 K per day, though impacts of the aerosol can be felt elsewhere in the atmospheric column. SW radiative heating due to biomass burning aerosol is not balanced by additional longwave cooling, and the net radiative impact results in a stabilization of the lower troposphere. However, these results are extremely sensitive to the single scatter albedo and the height of the aerosol plume with respect to the inversion layer.

Corrected TOGA COARE Sounding Humidity Data: Impact on Diagnosed Properties of Convection and Climate over the Warm Pool

2003 ◽  
Vol 16 (14) ◽  
pp. 2370-2384 ◽  
Author(s):  
Paul E. Ciesielski ◽  
Richard H. Johnson ◽  
Patrick T. Haertel ◽  
Junhong Wang
Keyword(s):  
Cloud Model ◽  
Convective Available Potential Energy ◽  
Vertical Motion ◽  
Warm Pool ◽  
Radiative Heating ◽  
Tropical Ocean ◽  
Toga Coare ◽  
Beneficial Impact ◽  
Corrected Data ◽  
The Difference

Abstract This study reports on the humidity corrections in the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) upper-air sounding dataset and their impact on diagnosed properties of convection and climate over the warm pool. During COARE, sounding data were collected from 29 sites with Vaisala-manufactured systems and 13 sites with VIZ-manufactured systems. A recent publication has documented the characteristics of the humidity errors at the Vaisala sites and a procedure to correct them. This study extends that work by describing the nature of the VIZ humidity errors and their correction scheme. The corrections, which are largest in lower-tropospheric levels, generally increase the moisture in the Vaisala sondes and decrease it in the VIZ sondes. Use of the corrected humidity data gives a much different perspective on the characteristics of convection during COARE. For example, application of a simple cloud model shows that the peak in convective mass flux shifts from about 8°N with the uncorrected data to just south of the equator with corrected data, which agrees better with the diagnosed vertical motion and observed rainfall. Also, with uncorrected data the difference in mean convective available potential energy (CAPE) between Vaisala and VIZ sites is over 700 J kg−1; with the correction, both CAPEs are around ∼1300 J kg−1, which is consistent with a generally uniform warm pool SST field. These results suggest that the intensity and location of convection would differ significantly in model simulations with humidity-corrected data, and that the difficulties which the reanalysis products had in reproducing the observed rainfall during COARE may be due to the sonde humidity biases. The humidity-corrected data appear to have a beneficial impact on budget-derived estimates of rainfall and radiative heating rate, such that revised estimates show better agreement with those from independent sources.

scholarly journals Evaluation of radiative heating rate profiles in eight GCMs using A-train satellite observations

2017 ◽  
Author(s):  
Gregory Cesana ◽  
D. E. Waliser ◽  
T. L’Ecuyer ◽  
X. Jiang ◽  
J.-L. Li
Keyword(s):  
Heating Rate ◽  
Satellite Observations ◽  
Radiative Heating
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