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  • Author or Editor: P. K. Bhartia x
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Omar Torres
,
Hiren Jethva
, and
P. K. Bhartia

Abstract

A large fraction of the atmospheric aerosol load reaching the free troposphere is frequently located above low clouds. Most commonly observed aerosols above clouds are carbonaceous particles generally associated with biomass burning and boreal forest fires, and mineral aerosols originating in arid and semiarid regions and transported across large distances, often above clouds. Because these aerosols absorb solar radiation, their role in the radiative transfer balance of the earth–atmosphere system is especially important. The generally negative (cooling) top-of-the-atmosphere direct effect of absorbing aerosols may turn into warming when the light-absorbing particles are located above clouds. The actual effect depends on the aerosol load and the single scattering albedo, and on the geometric cloud fraction. In spite of its potential significance, the role of aerosols above clouds is not adequately accounted for in the assessment of aerosol radiative forcing effects due to the lack of measurements. This paper discusses the basis of a simple technique that uses near-UV observations to simultaneously derive the optical depth of both the aerosol layer and the underlying cloud for overcast conditions. The two-parameter retrieval method described here makes use of the UV aerosol index and reflectance measurements at 388 nm. A detailed sensitivity analysis indicates that the measured radiances depend mainly on the aerosol absorption exponent and aerosol–cloud separation. The technique was applied to above-cloud aerosol events over the southern Atlantic Ocean, yielding realistic results as indicated by indirect evaluation methods. An error analysis indicates that for typical overcast cloudy conditions and aerosol loads, the aerosol optical depth can be retrieved with an accuracy of approximately 54% whereas the cloud optical depth can be derived within 17% of the true value.

Full access
K. F. Klenk
,
P. K. Bhartia
,
E. Hilsenrath
, and
A. J. Fleig

Abstract

Standard profiles based on upper level averaged profiles From BUV and lower level averaged profiles from balloon measurements are presented in a parametric representation as a function of time of year and latitude. The representation is a simple 4-parameter function representing the ozone amount (m-atm-cm) in each of 12 atmospheric layers defined following the standard Umkehr convention. The same parameterization is applied to the Nimbus-7 SBUV data and is compared to the BUV/balloon parameterization. The ozone variance unaccounted for by the representation is presented and discussed. The season-latitude representation reduces considerably the ozone variance at all levels and explains much of the correlation between layers. This simple representation and corresponding covariance matrix have been used as a priori information in the ozone vertical profile inversion of the Nimbus-7 SBUV experimental measurements.

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O. Torres
,
P. K. Bhartia
,
J. R. Herman
,
A. Sinyuk
,
Paul Ginoux
, and
Brent Holben

Abstract

Observations of backscattered near-ultraviolet radiation from the Total Ozone Mapping Spectrometer (TOMS) on board the Nimbus-7 (1979–92) and the Earth Probe (mid-1996 to present) satellites have been used to derive a long-term record of aerosol optical depth over oceans and continents. The retrieval technique applied to the TOMS data makes use of two unique advantages of near-UV remote sensing not available in the visible or near-IR: 1) low reflectivity of all land surface types (including the normally bright deserts in the visible), which makes possible aerosol retrieval over the continents; and 2) large sensitivity to aerosol types that absorb in the UV, allowing the clear separation of carbonaceous and mineral aerosols from purely scattering particles such as sulfate and sea salt aerosols. The near-UV method of aerosol characterization is validated by comparison with Aerosol Robotic Network (AERONET) ground-based observations. TOMS retrievals of aerosol optical depth over land areas (1996–2000) are shown to agree reasonably well with AERONET sun photometer observations for a variety of environments characterized by different aerosol types, such as carbonaceous aerosols from biomass burning, desert dust aerosols, and sulfate aerosols. In most cases the TOMS-derived optical depths of UV-absorbing aerosols are within 30% of the AERONET observations, while nonabsorbing optical depths agree to within 20%. The results presented here constitute the first long-term nearly global climatology of aerosol optical depth over both land and water surfaces, extending the observations of aerosol optical depth to regions and times (1979 to present) not accessible to ground-based observations.

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K. F. Klenk
,
P. K. Bhartia
,
V. G. Kaveeshwar
,
R. D. McPeters
,
P. M. Smith
, and
A. J. Fleig

Abstract

The algorithm used to derive total ozone from the Nimbus 4 Backscattered Ultraviolet (BUV) experiment is described. A seven-year global data set with more than one million retrievals has been produced and archived using this algorithm. The algorithm is a physical retrieval scheme using accurate radiative transfer computations. Error sources are discussed and verified using Dobson network comparisons and the statistics of the BUV A- and B-pair derived ozone values.

Full access
Clark Weaver
,
Dong L. Wu
,
P. K. Bhartia
,
Gordon Labow
,
David P. Haffner
,
Lauren Borgia
,
Laura McBride
, and
Ross Salawitch

Abstract

We construct a long-term record of top of atmosphere (TOA) shortwave (SW) albedo of clouds and aerosols from 340-nm radiances observed by NASA and NOAA satellite instruments from 1980 to 2013. We compare our SW cloud+aerosol albedo with simulated cloud albedo from both AMIP and historical CMIP6 simulations from 47 climate models. While most historical runs did not simulate our observed spatial pattern of the trends in albedo over the Pacific Ocean, four models qualitatively simulate our observed patterns. Those historical models and the AMIP models collectively estimate an equilibrium climate sensitivity (ECS) of ∼3.5°C, with an uncertainty from 2.7° to 5.1°C. Our ECS estimates are sensitive to the instrument calibration, which drives the wide range in ECS uncertainty. We use instrument calibrations that assume a neutral change in reflectivity over the Antarctic ice sheet. Our observations show increasing cloudiness over the eastern equatorial Pacific and off the coast of Peru as well as neutral cloud trends off the coast of Namibia and California. To produce our SW cloud+aerosol albedo, we first retrieve a black-sky cloud albedo (BCA) and empirically correct the sampling bias from diurnal variations. Then, we estimate the broadband proxy albedo using multiple nonlinear regression along with several years of CERES cloud albedo to obtain the regression coefficients. We validate our product against CERES data from the years not used in the regression. Zonal mean trends of our SW cloud+aerosol albedo show reasonable agreement with CERES as well as the Pathfinder Atmospheres–Extended (PATMOS-x) observational dataset.

Significance Statement

Equilibrium climate sensitivity is a measure of the rise in global temperature over hundreds of years after a doubling of atmospheric CO2 concentration. Current state-of-the-art climate models forecast a wide range of equilibrium climate sensitivities (1.5°–6°C), due mainly to how clouds, aerosols, and sea surface temperatures are simulated within these models. Using data from NASA and NOAA satellite instruments from 1980 to 2013, we first construct a dataset that describes how much sunlight has been reflected by clouds over the 34 years and then we compare this data record to output from 47 climate models. Based on these comparisons, we conclude the best estimate of equilibrium climate sensitivity is about 3.5°C, with an uncertainty range of 2.7°–5.1°C.

Open access
S. A. Ackerman
,
S. Platnick
,
P. K. Bhartia
,
B. Duncan
,
T. L’Ecuyer
,
A. Heidinger
,
G. Skofronick-Jackson
,
N. Loeb
,
T. Schmit
, and
N. Smith

Abstract

Satellite meteorology is a relatively new branch of the atmospheric sciences. The field emerged in the late 1950s during the Cold War and built on the advances in rocketry after World War II. In less than 70 years, satellite observations have transformed the way scientists observe and study Earth. This paper discusses some of the key advances in our understanding of the energy and water cycles, weather forecasting, and atmospheric composition enabled by satellite observations. While progress truly has been an international achievement, in accord with a monograph observing the centennial of the American Meteorological Society, as well as limited space, the emphasis of this chapter is on the U.S. satellite effort.

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S. Kondragunta
,
L. E. Flynn
,
A. Neuendorffer
,
A. J. Miller
,
C. Long
,
R. Nagatani
,
S. Zhou
,
T. Beck
,
E. Beach
,
R. McPeters
,
R. Stolarski
,
P. K. Bhartia
,
M. T. DeLand
, and
L.-K. Huang

Abstract

Ozone estimates from observations by the NOAA-16 Solar Backscattered Ultraviolet (SBUV/2) instrument and Television Infrared Observation Satellite (TIROS-N) Operational Vertical Sounder (TOVS) are used to describe the vertical structure of ozone in the anomalous 2002 polar vortex. The SBUV/2 total ozone maps show that the ozone hole was pushed off the Pole and split into two halves due to a split in the midstratospheric polar vortex in late September. The vortex split and the associated transport of high ozone from midlatitudes to the polar region reduced the ozone hole area from 18 × 106 km2 on 20 September to 3 × 106 km2 on 27 September 2002. A 23-yr time series of SBUV/2 daily zonal mean total ozone amounts between 70° and 80°S shows record high values [385 Dobson units (DU)] during the late-September 2002 warming event. The transport and descent of high ozone from low latitudes to high latitudes between 60 and 15 mb contributed to the unusual increase in total column ozone and a small ozone hole estimated using the standard criterion (area with total ozone < 220 DU). In contrast, TOVS observations show an ozone-depleted region between 0 and 24 km, indicating that ozone destruction was present in the elongated but unsplit vortex in the lower stratosphere. During the warming event, the low-ozone regions in the middle and upper stratosphere were not vertically aligned with the low-ozone regions in the upper troposphere and lower stratosphere. This offset in the vertical distribution of ozone resulted in higher total column ozone masking the ozone depletion in the lower stratosphere and resulting in a smaller ozone hole size estimate from satellite total ozone data.

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Jhoon Kim
,
Ukkyo Jeong
,
Myoung-Hwan Ahn
,
Jae H. Kim
,
Rokjin J. Park
,
Hanlim Lee
,
Chul Han Song
,
Yong-Sang Choi
,
Kwon-Ho Lee
,
Jung-Moon Yoo
,
Myeong-Jae Jeong
,
Seon Ki Park
,
Kwang-Mog Lee
,
Chang-Keun Song
,
Sang-Woo Kim
,
Young Joon Kim
,
Si-Wan Kim
,
Mijin Kim
,
Sujung Go
,
Xiong Liu
,
Kelly Chance
,
Christopher Chan Miller
,
Jay Al-Saadi
,
Ben Veihelmann
,
Pawan K. Bhartia
,
Omar Torres
,
Gonzalo González Abad
,
David P. Haffner
,
Dai Ho Ko
,
Seung Hoon Lee
,
Jung-Hun Woo
,
Heesung Chong
,
Sang Seo Park
,
Dennis Nicks
,
Won Jun Choi
,
Kyung-Jung Moon
,
Ara Cho
,
Jongmin Yoon
,
Sang-kyun Kim
,
Hyunkee Hong
,
Kyunghwa Lee
,
Hana Lee
,
Seoyoung Lee
,
Myungje Choi
,
Pepijn Veefkind
,
Pieternel F. Levelt
,
David P. Edwards
,
Mina Kang
,
Mijin Eo
,
Juseon Bak
,
Kanghyun Baek
,
Hyeong-Ahn Kwon
,
Jiwon Yang
,
Junsung Park
,
Kyung Man Han
,
Bo-Ram Kim
,
Hee-Woo Shin
,
Haklim Choi
,
Ebony Lee
,
Jihyo Chong
,
Yesol Cha
,
Ja-Ho Koo
,
Hitoshi Irie
,
Sachiko Hayashida
,
Yasko Kasai
,
Yugo Kanaya
,
Cheng Liu
,
Jintai Lin
,
James H. Crawford
,
Gregory R. Carmichael
,
Michael J. Newchurch
,
Barry L. Lefer
,
Jay R. Herman
,
Robert J. Swap
,
Alexis K. H. Lau
,
Thomas P. Kurosu
,
Glen Jaross
,
Berit Ahlers
,
Marcel Dobber
,
C. Thomas McElroy
, and
Yunsoo Choi

Abstract

The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled for launch in February 2020 to monitor air quality (AQ) at an unprecedented spatial and temporal resolution from a geostationary Earth orbit (GEO) for the first time. With the development of UV–visible spectrometers at sub-nm spectral resolution and sophisticated retrieval algorithms, estimates of the column amounts of atmospheric pollutants (O3, NO2, SO2, HCHO, CHOCHO, and aerosols) can be obtained. To date, all the UV–visible satellite missions monitoring air quality have been in low Earth orbit (LEO), allowing one to two observations per day. With UV–visible instruments on GEO platforms, the diurnal variations of these pollutants can now be determined. Details of the GEMS mission are presented, including instrumentation, scientific algorithms, predicted performance, and applications for air quality forecasts through data assimilation. GEMS will be on board the Geostationary Korea Multi-Purpose Satellite 2 (GEO-KOMPSAT-2) satellite series, which also hosts the Advanced Meteorological Imager (AMI) and Geostationary Ocean Color Imager 2 (GOCI-2). These three instruments will provide synergistic science products to better understand air quality, meteorology, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution will increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than is possible from LEO. GEMS will be joined by NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO) and ESA’s Sentinel-4 to form a GEO AQ satellite constellation in early 2020s, coordinated by the Committee on Earth Observation Satellites (CEOS).

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