scholarly journals A non-iterative linear retrieval for infrared high resolution limb sounders

2013 ◽  
Vol 6 (1) ◽  
pp. 721-766
Author(s):  
L. Millán ◽  
A. Dudhia
Keyword(s):  
High Resolution ◽  
Computing Time ◽  
Michelson Interferometer ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Spectral Signature ◽  
Transfer Model ◽  
Gas Concentration ◽  
Atmospheric Sounding ◽  
Retrieval Scheme

Abstract. Currently most of the high spectral resolution infrared limb sounders use subsets of the recorded spectra (microwindows) in their retrieval schemes to reduce the computing time of rerunning the radiative transfer model. A fast linear retrieval scheme is described which allows the whole spectral signature of the target molecule to be used. We determine how close the linearisation point needs to be to the solution in order to fall in the linear regime and also suggest an adjustment to the forward model and Jacobians to propagate the change in pressure and temperature on the gas concentration retrievals. As an example, this technique is implemented for the Michelson Interferometer for Passive Atmospheric Sounding instrument, but it is applicable to any high resolution limb sounder.

scholarly journals A non-iterative linear retrieval for infrared high-resolution limb sounders

2013 ◽  
Vol 6 (5) ◽  
pp. 1381-1396
Author(s):  
L. Millán ◽  
A. Dudhia
Keyword(s):  
High Resolution ◽  
Computing Time ◽  
Michelson Interferometer ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Spectral Signature ◽  
Transfer Model ◽  
Concentration Difference ◽  
Error Margin ◽  
Retrieval Scheme

Abstract. Currently, most of the high-spectral-resolution infrared limb sounders use subsets of the recorded spectra (microwindows) in their retrieval schemes to reduce the computing time of rerunning the radiative transfer model. A fast linear retrieval scheme is described which allows the whole spectral signature of the target molecule to be used. We determine that pressure and temperature retrievals can be treated linearly up to a 20% difference between the atmospheric state and the linearisation point for a 3% error margin and up to 10 K "difference" for a 3 K error margin near the stratopause and less than 0.5 K elsewhere. Assuming perfect pT knowledge, CH4 retrievals can be be treated linearly up to a 20% CH4 concentration "difference" for a 2% error margin. As an example, this technique is implemented for the Michelson Interferometer for Passive Atmospheric Sounding instrument, but it is applicable to any high-resolution limb sounder.

scholarly journals MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP

2012 ◽  
Vol 5 (10) ◽  
pp. 2537-2553 ◽  
Author(s):  
H. Sembhi ◽  
J. Remedios ◽  
T. Trent ◽  
D. P. Moore ◽  
R. Spang ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Detection System ◽  
Michelson Interferometer ◽  
Detection Limits ◽  
Infrared Emission ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Particle Injection

Abstract. Satellite infrared emission instruments require efficient systems that can separate and flag observations which are affected by clouds and aerosols. This paper investigates the identification of cloud and aerosols from infrared, limb sounding spectra that were recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a high spectral resolution Fourier transform spectrometer on the European Space Agency's (ESA) ENVISAT (Now inoperative since April 2012 due to loss of contact). Specifically, the performance of an existing cloud and aerosol particle detection method is simulated with a radiative transfer model in order to establish, for the first time, confident detection limits for particle presence in the atmosphere from MIPAS data. The newly established thresholds improve confidence in the ability to detect particle injection events, plume transport in the upper troposphere and lower stratosphere (UTLS) and better characterise cloud distributions utilising MIPAS spectra. The method also provides a fast front-end detection system for the MIPClouds processor; a processor designed for the retrieval of macro- and microphysical cloud properties from the MIPAS data. It is shown that across much of the stratosphere, the threshold for the standard cloud index in band A is 5.0 although threshold values of over 6.0 occur in restricted regimes. Polar regions show a surprising degree of uncertainty at altitudes above 20 km, potentially due to changing stratospheric trace gas concentrations in polar vortex conditions and poor signal-to-noise due to cold atmospheric temperatures. The optimised thresholds of this study can be used for much of the time, but time/composition-dependent thresholds are recommended for MIPAS data for the strongly perturbed polar stratosphere. In the UT, a threshold of 5.0 applies at 12 km and above but decreases rapidly at lower altitudes. The new thresholds are shown to allow much more sensitive detection of particle distributions in the UTLS, with extinction detection limits above 13 km often better than 10−4 km−1, with values approaching 10−5 km−1 in some cases. Comparisons of the new MIPAS results with cloud data from HIRDLS and CALIOP, outside of the poles, establish a good agreement in distributions (cloud and aerosol top heights and occurrence frequencies) with an offset between MIPAS and the other instruments of 0.5 km to 1 km between 12 km and 20 km, consistent with vertical oversampling of extended cloud layers within the MIPAS field of view. We conclude that infrared limb sounders provide a very consistent picture of particles in the UTLS, allowing detection limits which are consistent with the lidar observations. Investigations of MIPAS data for the Mount Kasatochi volcanic eruption on the Aleutian Islands and the Black Saturday fires in Australia are used to exemplify how useful MIPAS limb sounding data were for monitoring aerosol injections into the UTLS. It is shown that the new thresholds allowed such events to be much more effectively derived from MIPAS with detection limits for these case studies of 1 × 10−5 km−1 at a wavelength of 12 μm.

scholarly journals Global distributions and trends of atmospheric ammonia (NH<sub>3</sub>) from IASI satellite observations

2013 ◽  
Vol 13 (9) ◽  
pp. 24301-24342 ◽  
Author(s):  
M. Van Damme ◽  
L. Clarisse ◽  
C. L. Heald ◽  
D. Hurtmans ◽  
Y. Ngadi ◽  
...  
Keyword(s):  
Radiative Transfer Model ◽  
Local Source ◽  
Transfer Model ◽  
Error Characterization ◽  
Atmospheric Sounding ◽  
Retrieval Scheme ◽  
Transport Patterns ◽  
Computational Resources ◽  
Regional Budgets ◽  
Northern And Southern Hemispheres

Abstract. Ammonia (NH3) emissions in the atmosphere have strongly increased in the past decades, largely because of the intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except in and close to local source areas. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800–1200 cm−1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up-tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily, above both land and sea, without large computational resources and with an improved detection limit. The retrieval also provides error characterization on the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year dataset of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years dataset are provided and analyzed at global and regional scales. We show in particular the ability of this method to identify smaller emission sources than those reported previously, as well as transport patterns above sea. The five year time series is further examined in terms of seasonality and inter-annual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

scholarly journals MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP

2012 ◽  
Vol 5 (1) ◽  
pp. 1795-1841 ◽  
Author(s):  
H. Sembhi ◽  
J. Remedios ◽  
T. Trent ◽  
D. P. Moore ◽  
R. Spang ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Detection System ◽  
Michelson Interferometer ◽  
Detection Limits ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Particle Injection ◽  
Infra Red

Abstract. Satellite infra-red emission instruments require efficient systems that can separate and flag observations which are affected by clouds and aerosols. This paper investigates the identification of cloud and aerosols from infra-red, limb sounding spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a high spectral resolution, Fourier transform spectrometer on ENVISAT. Specifically, the performance of an existing cloud and aerosol particle detection method is simulated, with a radiative transfer model, in order to establish for the first time limits to confident detection of particle effects in MIPAS data. The newly established thresholds improve confidence in the ability of MIPAS to detect particle injection events and plume transport in the UTLS as well as better characterised cloud distributions. The method also provides a fast front-end detection system for the MIPClouds processor, a processor designed for the retrieval of macro- and microphysical cloud properties from the MIPAS data. It is shown that across much of the stratosphere, the threshold for the standard cloud index in band A is 5 although values of greater than 6 occur in restricted regimes. Polar regions show a surprising degree of uncertainty at altitudes above 20 km due to potential high ClO formation and also poor signal-to-noise due to low atmosphere temperatures. The optimised thresholds of this study can be used for much of the time, but time/composition dependent thresholds are recommended for MIPAS data for the strongly perturbed polar stratosphere. In the UT, thresholds of 5 apply at 12 km and above but decrease rapidly at lower altitudes. The new thresholds are shown to allow much more sensitive detection of particle distributions in the upper troposphere and lower stratosphere (UTLS), with extinction detection limits above 13 km often better than 10−4 km−1, with values approaching 10−5 km−1 in some cases. Comparisons of the new MIPAS results with data from HIRDLS and CALIOP, outside of the poles, establishes good agreement in distributions (cloud occurrence frequencies and clouds and aerosol top heights) with an offset between MIPAS and the other instruments of 0.5 km between 12 and 20 km. We conclude that current infra-red limb sounders provide a very consistent picture of particles in the UTLS, allowing detection limits which are consistent with the lidar observations. Investigations of the MIPAS data for the Kasatochi volcanic eruption and the Black Saturday fires in Australia are used to exemplify the usefulness of MIPAS limb sounding data for monitoring aerosol injections into the UTLS, and into the stratosphere, in particular over monthly timescales. It is shown that the new thresholds allow such events to be much more effectively monitored from MIPAS with detection limits for these case studies of 1 × 10−5 km−1 at 12 μm.

Dependence of Simulation Biases at AHI Surface-Sensitive Channels on Land Surface Emissivity over China

2018 ◽  
Vol 35 (6) ◽  
pp. 1283-1298 ◽  
Author(s):  
X. Zhuge ◽  
X. Zou ◽  
F. Weng ◽  
M. Sun
Keyword(s):  
Brightness Temperature ◽  
Spectral Resolution ◽  
Land Surface ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Surface Emissivity ◽  
Bare Rock ◽  
Land Surface Emissivity ◽  
M Channels

AbstractThis study compares the simulation biases of Advanced Himawari Imager (AHI) brightness temperature to observations made at night over China through the use of three land surface emissivity (LSE) datasets. The University of Wisconsin–Madison High Spectral Resolution Emissivity dataset, the Combined Advanced Spaceborne Thermal Emission and Reflection Radiometer and Moderate Resolution Imaging Spectroradiometer Emissivity database over Land High Spectral Resolution Emissivity dataset, and the International Geosphere–Biosphere Programme (IGBP) infrared LSE module, as well as land skin temperature observations from the National Basic Meteorological Observing stations in China are used as inputs to the Community Radiative Transfer Model. The results suggest that the standard deviations of AHI observations minus background simulations (OMBs) are largely consistent for the three LSE datasets. Also, negative biases of the OMBs of brightness temperature uniformly occur for each of the three datasets. There are no significant differences in OMB biases estimated with the three LSE datasets over cropland and forest surface types for all five AHI surface-sensitive channels. Over the grassland surface type, significant differences (~0.8 K) are found at the 10.4-, 11.2-, and 12.4-μm channels if using the IGBP dataset. Over nonvegetated surface types (e.g., sandy land, gobi, and bare rock), the lack of a monthly variation in IGBP LSE introduces large negative biases for the 3.9- and 8.6-μm channels, which are greater than those from the two other LSE datasets. Thus, improvements in simulating AHI infrared surface-sensitive channels can be made when using spatially and temporally varying LSE estimates.

scholarly journals Vertical level selection for temperature and trace gas profile retrievals using IASI

2015 ◽  
Vol 8 (6) ◽  
pp. 2359-2369 ◽  
Author(s):  
R. A. Vincent ◽  
A Dudhia ◽  
L. J. Ventress
Keyword(s):  
Trace Gas ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Infrared Observation ◽  
Atmospheric Sounding ◽  
Selection For ◽  
Vertical Spacing ◽  
Vertical Level ◽  
New Iterative Method ◽  
Grid Based

Abstract. This work presents a new iterative method for optimally selecting a vertical retrieval grid based on the location of the information while accounting for inter-level correlations. Sample atmospheres initially created to parametrise the Radiative Transfer Model for the Television Infrared Observation Satellite Operational Vertical Sounder (RTTOV) forward model are used to compare the presented iterative selection method with two other common approaches, which are using levels of equal vertical spacing and selecting levels based on the cumulative trace of the averaging kernel matrix (AKM). This new method is shown to outperform compared methods for simulated profile retrievals of temperature, H2O, O3, CH4, and CO with the Infrared Atmospheric Sounding Interferometer (IASI). However, the benefits of using the more complicated iterative approach compared to the simpler cumulative trace method are slight and may not justify the added effort for the cases studied, but may be useful in other scenarios where temperature and trace gases have strong vertical gradients with significant estimate sensitivity. Furthermore, comparing retrievals using a globally optimised static grid vs. a locally adapted one shows that a static grid performs nearly as well for retrievals of O3, CH4, and CO. However, developers of temperature and H2O retrieval schemes may at least consider using adaptive or location specific vertical retrieval grids.

scholarly journals Analysis of new species retrieved from MIPAS

2014 ◽  
Vol 56 ◽  
Author(s):  
Shaomin Cai ◽  
Anu Dudhia
Keyword(s):  
Fourier Transform ◽  
New Species ◽  
High Resolution ◽  
Trace Gases ◽  
Michelson Interferometer ◽  
Emission Spectra ◽  
Fourier Transform Spectrometer ◽  
Mid Infrared ◽  
The Third ◽  
Atmospheric Sounding

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument which operated on the Envisat satellite from 2002-2012 is a Fourier transform spectrometer for the measurement of high-resolution gaseous emission spectra at the Earth's limb. It operates in the near- to mid-infrared, where many of the main atmospheric trace gases have important emission features. The initial operational products were profiles of Temperature, H2O, O3, CH4, N2O, HNO3, and NO2, and this list was recently extended to include N2O5, ClONO2, CFC-11 and CFC-12. Here we present preliminary results of retrievals of the third set of species under consideration for inclusion in the operational processor: HCN, CF4, HCFC-22, COF2 and CCl4.

scholarly journals Bias determination and precision validation of ozone profiles from MIPAS-Envisat retrieved with the IMK-IAA processor

2007 ◽  
Vol 7 (13) ◽  
pp. 3639-3662 ◽  
Author(s):  
T. Steck ◽  
T. von Clarmann ◽  
H. Fischer ◽  
B. Funke ◽  
N. Glatthor ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Michelson Interferometer ◽  
High Spectral Resolution ◽  
Vapor Concentration ◽  
Atmospheric Sounding ◽  
Mean Differences ◽  
Microwave Radiometers ◽  
Vertical Ozone ◽  
Vertical Ozone Profiles ◽  
Polar Ozone

Abstract. This paper characterizes vertical ozone profiles retrieved with the IMK-IAA (Institute for Meteorology and Climate Research, Karlsruhe – Instituto de Astrofisica de Andalucia) science-oriented processor from high spectral resolution data (until March 2004) measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the environmental satellite Envisat. Bias determination and precision validation is performed on the basis of correlative measurements by ground-based lidars, Fourier transform infrared spectrometers, and microwave radiometers as well as balloon-borne ozonesondes, the balloon-borne version of MIPAS, and two satellite instruments (Halogen Occultation Experiment and Polar Ozone and Aerosol Measurement III). Percentage mean differences between MIPAS and the comparison instruments for stratospheric ozone are generally within ±10%. The precision in this altitude region is estimated at values between 5 and 10% which gives an accuracy of 15 to 20%. Below 18 km, the spread of the percentage mean differences is larger and the precision degrades to values of more than 20% depending on altitude and latitude. The main reason for the degraded precision at low altitudes is attributed to undetected thin clouds which affect MIPAS retrievals, and to the influence of uncertainties in the water vapor concentration.

scholarly journals High resolution and Monte Carlo additions to the SASKTRAN radiative transfer model

2015 ◽  
Vol 8 (3) ◽  
pp. 3357-3397 ◽  
Author(s):  
D. J. Zawada ◽  
S. R. Dueck ◽  
L. A. Rieger ◽  
A. E. Bourassa ◽  
N. D. Lloyd ◽  
...  
Keyword(s):  
Monte Carlo ◽  
High Resolution ◽  
Radiative Transfer ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Reference Model ◽  
Monte Carlo Model ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Systematic Bias

Abstract. The OSIRIS instrument on board the Odin spacecraft has been measuring limb scattered radiance since 2001. The vertical radiance profiles measured as the instrument nods are inverted, with the aid of the SASKTRAN radiative transfer model, to obtain vertical profiles of trace atmospheric constituents. Here we describe two newly developed modes of the SASKTRAN radiative transfer model: a high spatial resolution mode, and a Monte Carlo mode. The high spatial resolution mode is a successive orders model capable of modelling the multiply scattered radiance when the atmosphere is not spherically symmetric; the Monte Carlo mode is intended for use as a highly accurate reference model. It is shown that the two models agree in a wide variety of solar conditions to within 0.2%. As an example case for both models, Odin-OSIRIS scans were simulated with the Monte Carlo model and retrieved using the high resolution model. A systematic bias of up to 4% in retrieved ozone number density between scans where the instrument is scanning up or scanning down was identified. It was found that calculating the multiply scattered diffuse field at five discrete solar zenith angles is sufficient to eliminate the bias for typical Odin-OSIRIS geometries.

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