scholarly journals Revisiting the Relationship between Atlantic Dust and Tropical Cyclone Activity using Aerosol Optical Depth Reanalyses: 2003–2018

2020 ◽  
Author(s):  
Peng Xian ◽  
Philip J. Klotzbach ◽  
Jason P. Dunion ◽  
Matthew A. Janiga ◽  
Jeffrey S. Reid ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
North Atlantic ◽  
Large Scale ◽  
Tropical Atlantic ◽  
African Dust ◽  
Tropical North Atlantic ◽  
June July ◽  
The Relationship

Abstract. Previous studies have noted a relationship between African dust and Atlantic tropical cyclone (TC) activity. However, due to the limitations of past dust analyses, the strength of this relationship remains uncertain. The emergence of aerosol reanalyses, including the Navy Aerosol Analysis and Prediction System (NAAPS) Aerosol Optical Depth (AOD) reanalysis, NASA Modern-Era Retrospective analysis for Research and Applications, Version-2 (MERRA-2) and ECMWF Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA) enable an investigation of the relationship between African dust and TC activity over the tropical Atlantic and Caribbean in a consistent temporal and spatial manner for 2003–2018. Although June-July-August (JJA) 550 nm dust AOD (DAOD) from all three reanalysis products correlate significantly over the tropical Atlantic and Caribbean, the difference in DAOD magnitude between products can be as large as 60 % over the Caribbean and 20 % over the tropical North Atlantic. Based on the three individual reanalyses, we have created an aerosol multi-reanalysis-consensus (MRC). The MRC presents overall better root mean square error over the tropical Atlantic and Caribbean compared to individual reanalyses when verified with ground-based AErosol RObotic NETwork (AERONET) AOD measurements. Each of the three individual reanalyses and the MRC have significant negative correlations between JJA Caribbean DAOD and seasonal Atlantic Accumulated Cyclone Energy (ACE), while the correlation between JJA tropical North Atlantic DAOD and seasonal ACE is weaker. Possible reasons for this regional difference are provided. A composite analysis of three high versus three low JJA Caribbean DAOD years reveals large differences in overall Atlantic TC activity. We also show that JJA Caribbean DAOD is significantly correlated with large-scale fields associated with variability in interannual Atlantic TC activity including zonal wind shear, mid-level moisture and SST, as well as ENSO and the Atlantic Meridional Mode (AMM), implying confounding effects of these factors on the dust-TC relationship. Further analysis indicates that seasonal Atlantic DAOD and the AMM, the leading mode of coupled Atlantic variability, are inversely related and intertwined in the dust-TC relationship.

scholarly journals Revisiting the relationship between Atlantic dust and tropical cyclone activity using aerosol optical depth reanalyses: 2003–2018

2020 ◽  
Vol 20 (23) ◽  
pp. 15357-15378
Author(s):  
Peng Xian ◽  
Philip J. Klotzbach ◽  
Jason P. Dunion ◽  
Matthew A. Janiga ◽  
Jeffrey S. Reid ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Tropical Atlantic ◽  
African Dust ◽  
Tropical North Atlantic ◽  
The Caribbean ◽  
The Relationship

Abstract. Previous studies have noted a relationship between African dust and Atlantic tropical cyclone (TC) activity. However, due to the limitations of past dust analyses, the strength of this relationship remains uncertain. The emergence of aerosol reanalyses, including the Navy Aerosol Analysis and Prediction System (NAAPS) aerosol optical depth (AOD) reanalysis, NASA Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and ECMWF Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA), enables an investigation of the relationship between African dust and TC activity over the tropical Atlantic and Caribbean in a consistent temporal and spatial manner for 2003–2018. Although June–July–August (JJA) 550 nm dust AOD (DAOD) from all three reanalysis products correlates significantly over the tropical Atlantic and Caribbean, the difference in DAOD magnitude between products can be as large as 60 % over the Caribbean and 20 % over the tropical North Atlantic. Based on the three individual reanalyses, we have created an aerosol multi-reanalysis consensus (MRC). The MRC presents overall better root mean square error over the tropical Atlantic and Caribbean compared to individual reanalyses when verified with ground-based AErosol RObotic NETwork (AERONET) AOD measurements. Each of the three individual reanalyses and the MRC have significant negative correlations between JJA Caribbean DAOD and seasonal Atlantic accumulated cyclone energy (ACE), while the correlation between JJA tropical North Atlantic DAOD and seasonal ACE is weaker. Possible reasons for this regional difference are provided. A composite analysis of 3 high-JJA-Caribbean-DAOD years versus 3 low-JJA-Caribbean-DAOD years reveals large differences in overall Atlantic TC activity. We also show that JJA Caribbean DAOD is significantly correlated with large-scale fields associated with variability in interannual Atlantic TC activity including zonal wind shear, mid-level moisture, and sea surface temperature (SST), as well as the El Niño–Southern Oscillation (ENSO) and the Atlantic Meridional Mode (AMM), implying confounding effects of these factors on the dust–TC relationship. We find that seasonal Atlantic DAOD and the AMM, the leading mode of coupled Atlantic variability, are inversely related and intertwined in the dust–TC relationship. Overall, DAOD in both the tropical Atlantic and Caribbean is negatively correlated with Atlantic hurricane frequency and intensity, with stronger correlations in the Caribbean than farther east in the tropical North Atlantic.

scholarly journals Moisture and Precipitation Evolution during Tropical Cyclone Formation as Revealed by the SSM/I–SSMIS Retrievals

2016 ◽  
Vol 73 (7) ◽  
pp. 2773-2781 ◽  
Author(s):  
Zhuo Wang ◽  
Isaac Hankes
Keyword(s):  
Water Vapor ◽  
Tropical Cyclone ◽  
North Atlantic ◽  
Deep Convection ◽  
Exponential Rate ◽  
Tropical Cyclone Formation ◽  
Time Period ◽  
Tropical North Atlantic ◽  
The Relationship ◽  
High Column

Abstract The simultaneous precipitation and column water vapor retrievals from the SSM/I and SSMIS passive microwave instruments were used to examine the convective and moisture evolution during tropical cyclone formation. Using a wave-pouch-track dataset, composites of precipitation and column water vapor were constructed with more than 2000 satellite overpasses for a 3-day time period prior to genesis. It was found that high column water vapor occurs near the pouch center and starts to increase about 42 h prior to genesis while a substantial increase in precipitation occurs within 24 h prior to genesis. These features are consistent with a recently proposed two-stage conceptual model for tropical cyclone formation, in which gradual moisture preconditioning precedes an abrupt transition to sustained deep convection leading up to genesis. The relationship between precipitation and saturation fraction (SF) is examined for the developing waves and compared with the general tropical North Atlantic. Precipitation rate is found to increase at the same exponential rate above the same critical point of SF in the two groups, but convection in the developing waves has a higher probability of occurrence near and above criticality. This can be attributed to the positive feedback between convection and the low-level moisture convergence, which counteracts the negative feedback of convection on water vapor and makes convection in a developing tropical cyclone more sustainable.

African Dust over the Northern Tropical Atlantic: 1955–2008

2010 ◽  
Vol 49 (11) ◽  
pp. 2213-2229 ◽  
Author(s):  
Amato T. Evan ◽  
Sujoy Mukhopadhyay
Keyword(s):  
Optical Depth ◽  
Annual Cycle ◽  
Radiative Forcing ◽  
Large Scale ◽  
Large Body ◽  
Dust Storms ◽  
Tropical Atlantic ◽  
Heating Rates ◽  
African Dust ◽  
Northern Tropical Atlantic

Abstract African dust outbreaks are the result of complex interactions between the land, atmosphere, and oceans, and only recently has a large body of work begun to emerge that aims to understand the controls on—and impacts of—African dust. At the same time, long-term records of dust outbreaks are either inferred from visibility data from weather stations or confined to a few in situ observational sites. Satellites provide the best opportunity for studying the large-scale characteristics of dust storms, but reliable records of dust are generally on the scale of a decade or less. Here the authors develop a simple model for using modern and historical data from meteorological satellites, in conjunction with a proxy record for atmospheric dust, to extend satellite-retrieved dust optical depth over the northern tropical Atlantic Ocean from 1955 to 2008. The resultant 54-yr record of dust has a spatial resolution of 1° and a monthly temporal resolution. From analysis of the historical dust data, monthly tropical northern Atlantic dust cover is bimodal, has a strong annual cycle, peaked in the early 1980s, and shows minimums in dustiness during the beginning and end of the record. These dust optical depth estimates are used to calculate radiative forcing and heating rates from the surface through the top of the atmosphere over the last half century. Radiative transfer simulations show a large net negative dust forcing from the surface through the top of the atmosphere, also with a distinct annual cycle, and mean tropical Atlantic monthly values of the surface forcing range from −3 to −9 W m−2. Since the surface forcing is roughly a factor of 3 larger in magnitude than the top-of-the-atmosphere forcing, there is also a positive heating rate of the midtroposphere by dust.

scholarly journals Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone

2012 ◽  
Vol 9 (10) ◽  
pp. 14291-14325 ◽  
Author(s):  
T. Fischer ◽  
D. Banyte ◽  
P. Brandt ◽  
M. Dengler ◽  
G. Krahmann ◽  
...  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Oxygen Supply ◽  
Water Layer ◽  
Oxygen Minimum Zone ◽  
Depth Interval ◽  
Diapycnal Mixing ◽  
Tropical North Atlantic ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. The replenishment of consumed oxygen in the open ocean oxygen minimum zone (OMZ) off West Africa in the tropical North Atlantic Ocean is studied, with a focus on oxygen transport across density surfaces (diapycnal flux). The latter is obtained from a large observational set of oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal mixing is inferred from different sources: a large scale tracer release experiment, microstructure profiles, and shipboard acoustic current measurements plus density profiles. The average diapycnal diffusivity in the study area is 1 × 10−5 m2 s−1. No significant vertical gradient of average diapycnal diffusivities exists in the depth interval from 150 to 500 m. The diapycnal flux is found to contribute substantially to the oxygen supply of the OMZ. Within the OMZ core, 1.5 µmol kg−1 a−1 of oxygen is supplied via diapycnal mixing, contributing about a third of the total demand. The oxygen that is contributed via diapycnal mixing originates from oxygen that has been laterally supplied within the overlying Central Water layer by advective and eddy fluxes. Due to the existence of a separate shallow oxygen minimum at about 100 m depth throughout most of the study area, there is no direct net vertical oxygen flux from the surface layer of the study area into the Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways.

scholarly journals Eurasia large-scale hazes in summer 2016

2019 ◽  
Vol 55 (3) ◽  
pp. 41-51
Author(s):  
G. I. Gorchakov ◽  
S. A. Sitnov ◽  
A. V. Karpov ◽  
I. A. Gorchakova ◽  
R. A. Gushchin ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Large Scale ◽  
Empirical Distribution ◽  
Growth Period ◽  
Maximum Growth ◽  
Qualitative Change ◽  
Smoke Aerosol

Using maximum aerosol optical depth (MAOD) spatial distribution formation technique the optically dense haze expansion scales in period from 15 to 31 July 2016 over Eurasia are estimated in during great Siberian smoke haze (SSH) with the area 16 mln km2 about, smog over the Northern China Plain (2 mln km2), dust haze in Takla Makan desert (0.8 mln km2) and hazes in India and Pakistan (1 mln km2 approximately). Empirical distribution function (EDF) MAOD is received which is approximated by linear function of MAOD logarithm. Aerosol optical depth (AOD) spatial distribution at wavelength 550 nm in SSH is analyzed. Total smoke aerosol mass assessment in SSH (3.2 mln tons) is evaluated. Smoke aerosol (SA) mass during maximum growth period from 22 July to 26 July 2016 over Siberia (50°-70°, 60°-120 °E) was equal 2 mln tons approximately. Aerosol index (AI) temporal variability is illustrated visually SA composition qualitative change in SSH during long-range transport. It is shown that AI variations are correlated with AOD variations. Aerosol radiative forcing (ARF) at the top and the bottom of the atmosphere over Siberia from 22 July to 26 July 2016 is estimated (average ARF are equal –68 and –98 W/m2). EDF AOD and EDF ARF at the top of the atmosphere are approximated by exponential and power function of AOD correspondingly.

Relationship between MODIS based Aerosol Optical Depth and PM10 over Croatia

2014 ◽  
Vol 6 (1) ◽  
Author(s):  
Sanja Grgurić ◽  
Josip Križan ◽  
Goran Gašparac ◽  
Oleg Antonić ◽  
Zdravko Špirić ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mass Concentration ◽  
Meteorological Data ◽  
Neural Network Approach ◽  
Data Set ◽  
Independent Variables ◽  
Data Variability ◽  
Modis Aod ◽  
The Relationship

AbstractThis study analyzes the relationship between Aerosol Optical Depth (AOD) obtained from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and ground-based PM10 mass concentration distribution over a period of 5 years (2008–2012), and investigates the applicability of satellite AOD data for ground PM10 mapping for the Croatian territory. Many studies have shown that satellite AOD data are correlated to ground-based PM mass concentration. However, the relationship between AOD and PM is not explicit and there are unknowns that cause uncertainties in this relationship.The relationship between MODIS AOD and ground-based PM10 has been studied on the basis of a large data set where daily averaged PM10 data from the 12 air quality stations across Croatia over the 5 year period are correlated with AODs retrieved from MODIS Terra and Aqua. A database was developed to associate coincident MODIS AOD (independent) and PM10 data (dependent variable). Additional tested independent variables (predictors, estimators) included season, cloud fraction, and meteorological parameters — including temperature, air pressure, relative humidity, wind speed, wind direction, as well as planetary boundary layer height — using meteorological data from WRF (Weather Research and Forecast) model.It has been found that 1) a univariate linear regression model fails at explaining the data variability well which suggests nonlinearity of the AOD-PM10 relationship, and 2) explanation of data variability can be improved with multivariate linear modeling and a neural network approach, using additional independent variables.

scholarly journals A Look at the Relationship between the Large-Scale Tropospheric Static Stability and the Tropical Cyclone Maximum Intensity

2020 ◽  
Vol 33 (3) ◽  
pp. 959-975
Author(s):  
Alexandria Downs ◽  
Chanh Kieu
Keyword(s):  
Tropical Cyclone ◽  
Negative Correlation ◽  
North Atlantic ◽  
Large Scale ◽  
Static Stability ◽  
Maximum Intensity ◽  
Northwestern Pacific ◽  
The North ◽  
The Future ◽  
The North Atlantic

AbstractVarious modeling and observational studies have suggested that tropical cyclone (TC) intensity tends to increase in the future due to projected warmer sea surface temperature (SST). This study examines the effects of the tropospheric stratification that could potentially offset the direct increase of TC intensity associated with the warmer SST. Using reanalysis datasets and TC records in the northwestern Pacific and the North Atlantic basins, it is shown that there exists a consistently negative correlation between the annually averaged TC intensity and the basinwide average of the tropospheric static stability. This negative correlation is more robust in the northwestern Pacific basin when using the TC lifetime maximum intensity but is somewhat less significant in the North Atlantic basin. Further separation of the troposphere into a lower (1000–500 hPa) and an upper layer (500–200 hPa) reveals that it is the upper-tropospheric static stability that plays a more dominant role in governing the TC intensity variability. The negating effects of a stable troposphere on TC intensity as found in this study suggest a partial offset of the projected increase in the TC potential intensity due to the future warmer SST. Thus, the tropospheric static stability is one of the key large-scale factors that need to be properly taken into account in studies of long-term TC intensity change.

scholarly journals Improved MODIS Dark Target aerosol optical depth algorithm over land: angular effect correction

2016 ◽  
Vol 9 (11) ◽  
pp. 5575-5589 ◽  
Author(s):  
Yerong Wu ◽  
Martin de Graaf ◽  
Massimo Menenti
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Vegetation Index ◽  
Surface Reflectance ◽  
Infrared Band ◽  
Surface Reflection ◽  
Global Land ◽  
Bidirectional Reflectance Factor ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Relationship

Abstract. Aerosol optical depth (AOD) product retrieved from MODerate Resolution Imaging Spectroradiometer (MODIS) measurements has greatly benefited scientific research in climate change and air quality due to its high quality and large coverage over the globe. However, the current product (e.g., Collection 6) over land needs to be further improved. The is because AOD retrieval still suffers large uncertainty from the surface reflectance (e.g., anisotropic reflection) although the impacts of the surface reflectance have been largely reduced using the Dark Target (DT) algorithm. It has been shown that the AOD retrieval over dark surface can be improved by considering surface bidirectional distribution reflectance function (BRDF) effects in previous study. However, the relationship of the surface reflectance between visible and shortwave infrared band that applied in the previous study can lead to an angular dependence of the AOD retrieval. This has at least two reasons. The relationship based on the assumption of isotropic reflection or Lambertian surface is not suitable for the surface bidirectional reflectance factor (BRF). However, although the relationship varies with the surface cover type by considering the vegetation index NDVISWIR, this index itself has a directional effect and affects the estimation of the surface reflection, and it can lead to some errors in the AOD retrieval. To improve this situation, we derived a new relationship for the spectral surface BRF in this study, using 3 years of data from AERONET-based Surface Reflectance Validation Network (ASRVN). To test the performance of the new algorithm, two case studies were used: 2 years of data from North America and 4 months of data from the global land. The results show that the angular effects of the AOD retrieval are largely reduced in most cases, including fewer occurrences of negative retrievals. Particularly, for the global land case, the AOD retrieval was improved by the new algorithm compared to the previous study and MODIS Collection 6 DT algorithm, with the increase of 2.0 and 4.5 % AOD retrievals falling within the expected accuracy envelope ±(0.05 + 15 %), respectively. This implies that the users can get more accurate data without angular bias, i.e., more meaningful AOD data.

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