[show abstract][hide abstract] ABSTRACT: 1] Atomic oxygen [O] plays a fundamental role in the photochemistry and energy budget of the terrestrial mesopause region (80–100 km). [O] is difficult to measure directly and is typically inferred at night from measurements of hydroxyl [OH] or molecular oxygen [O 2 ] emissions. During the day, measurements of ozone [O 3 ] concentration are used to infer [O]. These inferences carry significant uncertainties [Mlynczak et al., 2013a]. Recently, Mlynczak et al. [2013b] have used energy balance principles to set an upper limit on the annual global mean [O] concentration in the mesopause region. In this paper, we use night measurements of OH emission to set a lower limit on the global annual mean atomic oxygen concentration. These independent, radiatively constrained values of the maximum and minimum atomic oxygen concentration also place constraints on the magnitude of dynamical processes in the annual global mean energy budget of the mesopause region. Citation: Mlynczak, M. G., (2013), Radiative constraints on the minimum atomic oxygen concentration in the mesopause region, Geophys. Res. Lett., 40, doi:10.1002/grl.50725.
[show abstract][hide abstract] ABSTRACT: We present global distributions of v = 9 + v = 8 nighttime vibrationally
excited hydroxyl concentrations as measured by the SABER instrument on
board the TIMED spacecraft. These states are formed directly by the
reaction of atomic hydrogen and ozone in the terrestrial mesopause
region. SABER measures the limb radiance from the delta-v = 2
transitions in a channel centered near 2.0 um, specifically the sum of
the 9 -> 7 and 8 -> 6 transitions. The limb radiances are inverted
to yield the volume emission rates from the sum of the v = 8 and 9
states of the hydroxyl molecule. The Einstein coefficients for
spontaneous emission for these two transitions are essentially
identical. Thus dividing the derived volume emission rate by the
Einstein coefficient yields the absolute populations of these states
(molecules per cubic cm). Nine full years of data are presented in this
paper. Over this time the globally averaged OH(v = 8 + v = 9)
populations have varied relative to the nine year mean by only a few
percent. We conclude that despite substantial solar variability over
this time period, the apparently small variation of the highly
vibrationally excited hydroxyl populations implies that atomic hydrogen,
atomic oxygen, temperature, and density adjust in such a way so as to
keep the product of the atomic hydrogen concentration, the ozone
concentration, and the rate coefficient for their reaction essentially
[show abstract][hide abstract] ABSTRACT: We examine the annual energy budget of the mesosphere using measurements
from the SABER and SEE instruments on the TIMED satellite and from the
SORCE satellite. Rates of heating due to absorption of solar radiation
by ozone and molecular oxygen, rates of heating due to seven exothermic
chemical reactions, and rates of cooling due to infrared emission by
carbon dioxide and ozone are presented. A time series of radiative
cooling by carbon dioxide in the mesosphere for the past decade is also
included. While uncertainties, particularly in the rates of heating by
exothermic chemical reactions, place limits on the exact knowledge of
these parameters, we can show approximate balance in heating and cooling
rates on annual timescales.
[show abstract][hide abstract] ABSTRACT: The Sounding of the Atmosphere using Broadband Emission Radiometry
(SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere
Energetics and Dynamics (TIMED) satellite measures the vertical
distribution of infrared radiation emitted by various atmospheric gases,
including nitric oxide and carbon dioxide, providing important
information about the radiation budget in the upper atmosphere. From
these measurements, the infrared power and energy radiated by nitric
oxide (NO) and carbon dioxide (CO2) have been computed. The effects of
Solar Cycle 24 are now clearly evident in the infrared radiative cooling
of the thermosphere as observed by SABER. After reaching a minimum in
2009, infrared radiative cooling of the thermosphere by nitric oxide
(NO) and carbon dioxide (CO2) has been steadily increasing. The global
infrared power radiated by NO in mid-April 2011 is about four times the
minimum value while the CO2 power is about 15% larger than at the
minimum. In addition, the short-term variability of the NO emission has
increased and is strongly correlated with increased geomagnetic
variability as inferred from the Ap index. The increasing levels of
infrared emission are indicative of a warming thermosphere and possibly
increasing levels of atomic oxygen and nitric oxide. However the
infrared power presently radiated by NO is only about 40% of the maximum
value observed by the SABER instrument in late 2002 while the CO2 power
is now about 80% of the maximum observed value. The SABER infrared time
series, now approaching 10 years in length, is a unique climate data
record for testing the radiative and chemical physics of upper
atmosphere general circulation models.
Geophysical Research Letters 12/2011; · 3.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: Measurement of atmospheric temperature as a function of pressure, T(P), is key to understanding many atmospheric processes and a prerequisite for retrieving gas mixing ratios and other parameters from solar occultation measurements. This paper gives a brief overview of the solar occultation measurement technique followed by a detailed discussion of the mechanisms that make the measurement sensitive to temperature. Methods for retrieving T(P) using both broadband transmittance and refraction are discussed. Investigations using measurements of broadband transmittance in two CO2 absorption bands (the 4.3 and 2.7 μm bands) and refractive bending are then presented. These investigations include sensitivity studies, simulated retrieval studies, and examples from SOFIE.
[show abstract][hide abstract] ABSTRACT: The quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid (HNO3) and nitrogen dioxide (NO2) profiles and distributions of 1978/1979 is described after their processing with an updated, Version 6 (V6) algorithm and subsequent archival in 2002. Estimates of the precision and accuracy of both of those species are developed and provided herein. The character of the V6 HNO3 profiles is relatively unchanged from that of the earlier LIMS Version 5 (V5) profiles, except in the upper stratosphere where the interfering effects of CO2 are accounted for better with V6. The accuracy of the retrieved V6 NO2 is also significantly better in the middle and upper stratosphere, due to improvements in its spectral line parameters and in the reduced biases for the accompanying V6 temperature and water vapor profiles. As a result of these important updates, there is better agreement with theoretical calculations for profiles of the HNO3/NO2 ratio, day-to-night NO2 ratio, and with estimates of the production of NO2 in the mesosphere and its descent to the upper stratosphere during polar night. The improved precisions and more frequent retrievals of the profiles along the LIMS orbit tracks provide for better continuity and detail in map analyses of these two species on pressure surfaces. It is judged that the chemical effects of the oxides of nitrogen on ozone can be examined quantitatively throughout the stratosphere with the LIMS V6 data, and that the findings will be more compatible with those obtained from measurements of the same species from subsequent satellite sensors.
ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2010; · 5.51 Impact Factor
[show abstract][hide abstract] ABSTRACT: The SOFIE (Solar Occultation for Ice Experiment) instrument, launched on-board the AIM (Aeronomy of Ice in the Mesosphere) satellite on April 25, 2007, is in its third year of operation, and will enter a sixth polar summer ice season in November 2009. In addition to unprecedented sensitivity to ice, water and ozone in the upper mesosphere, SOFIE has produced several other remote sensing first-time achievements. Meteoric smoke is being measured over time and altitude. Temperature is being routinely retrieved with
[show abstract][hide abstract] ABSTRACT: This report describes the quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) water vapor (H2O) profiles of 1978/79 that were processed with a Version 6 (V6) algorithm and archived in 2002. The V6 profiles incorporate a better knowledge of the instrument attitude for the LIMS measurements along its orbits, leading to improvements for its temperature profiles and for the registration of its water vapor radiances with pressure. As a result, the LIMS V6 zonal-mean distributions of H2O exhibit better hemispheric symmetry than was the case from the original Version 5 (V5) dataset that was archived in 1982. Estimates of the precision and accuracy of the V6 H2O profiles are developed and provided. Individual profiles have a precision of order 5% and an estimated accuracy of about 19% at 3 hPa, 14% at 10 hPa, and 26% at 50 hPa. Profile segments within about 2 km of the tropopause are often affected by emissions from clouds that appear in the finite field-of-view of the detector for the LIMS H2O channel. Zonally-averaged distributions of the LIMS V6 H2O are compared with those from the more recent Microwave Limb Sounder (MLS) satellite experiment for November, February, and May of 2004/05. The patterns and values of their respective distributions are similar in many respects. Effects of a strengthened Brewer-Dobson circulation are indicated in the MLS distributions of the recent decade versus those of LIMS from 1978/79. A tropical tape recorder signal is present in the 7-month time series of LIMS V6 H2O with lowest values in February 1979, and the estimated, annually-averaged "entry-level" H2O is 3.5 to 3.8 ppmv. It is judged that this historic LIMS water vapor dataset is of good quality for studies of the near global-scale chemistry and transport for pressure levels from 3 hPa to about 70 to 100 hPa.
ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2009; · 5.51 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Halogen Occultation Experiment (HALOE) operated essentially without flaw on the Upper Atmosphere Research Satellite from the time it was first turned on in orbit October 11, 1991, until it was turned off in November 2005. HALOE measured temperature and a suite of atmospheric constituent vertical profiles including O3, HCl, HF, CH4, H2O, NO, NO2 and aerosol extinction at four wavelengths. Measurements of some of these parameters, i.e. O3, H2O, NO and temperature versus pressure, extend from the upper troposphere to well into the mesosphere and/or lower thermosphere. This study focuses on the HALOE 4th Public Release (v20). This data set provides the first complete HALOE H2O vertical profile results extending from the mid-to-upper troposphere to the upper mesosphere. The CH4, HCl, HF, and NO profiles have increased vertical resolution over the 3rd Public Release version and new line-by-line retrievals of O3 are included. We will present results of initial validation studies using mainly satellite correlative measurements and summarys of the inter-comparisons of some of the species with the previous data version, highlighting the changes and improvements in the latest public release.
[show abstract][hide abstract] ABSTRACT: The quality of retrieved profiles (e.g. mixing ratio, temperature, pressure, and extinction) from solar occultation sensors is strongly dependent on the angular fidelity of the measurements. The SOFIE instrument, launched on-board the AIM (Aeronomy of Ice in the Mesosphere) satellite on April 25, 2007, was designed to provide very high precision broadband measurements for the study of Polar Mesospheric Clouds (PMCs), that appear near 83km, just below the high latitude summer mesopause. The SOFIE instrument achieves an unprecedented angular fidelity by imaging the sun on a 2D detector array and tracking the edges with an uncertainty of
[show abstract][hide abstract] ABSTRACT: 1] The quality of the retrieved temperature-versus-pressure (or T(p)) profiles is described for the middle atmosphere for the publicly available Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) Version 1.07 (V1.07) data set. The primary sources of systematic error for the SABER results below about 70 km are (1) errors in the measured radiances, (2) biases in the forward model, and (3) uncertainties in the corrections for ozone and in the determination of the reference pressure for the retrieved profiles. Comparisons with other correlative data sets indicate that SABER T(p) is too high by 1–3 K in the lower stratosphere but then too low by 1 K near the stratopause and by 2 K in the middle mesosphere. There is little difference between the local thermodynamic equilibrium (LTE) algorithm results below about 70 km from V1.07 and V1.06, but there are substantial improvements/differences for the non-LTE results of V1.07 for the upper mesosphere and lower thermosphere (UMLT) region. In particular, the V1.07 algorithm uses monthly, diurnally averaged CO 2 profiles versus latitude from the Whole Atmosphere Community Climate Model. This change has improved the consistency of the character of the tides in its kinetic temperature (T k). The T k profiles agree with UMLT values obtained from ground-based measurements of column-averaged OH and O 2 emissions and of the Na lidar returns, at least within their mutual uncertainties. SABER T k values obtained near the mesopause with its daytime algorithm also agree well with the falling sphere climatology at high northern latitudes in summer. It is concluded that the SABER data set can be the basis for improved, diurnal-to-interannual-scale temperatures for the middle atmosphere and especially for its UMLT region.
Journal of Geophysical Research 01/2008; 113. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: Using a combination of data from the TIMED and SORCE satellites we have examined the macroscopic radiative energy balance of the atmosphere above 100 km. Time series of absorbed solar radiation from 0 to 120 nm and 120 to 175 nm have been developed. In addition, we compute the rates at which infrared energy is radiated by the atmosphere at 5.3 microns (by nitric oxide), 15 microns (by carbon dioxide), and 63 microns (atomic oxygen) using both measured emission rates and model computations. The effects of the declining phase of the current solar cycle are evident in the time series of both the absorbed solar radiation and the infrared emission at all wavelengths. In addition, spectral analyses yields several interesting periodic effects present in the infrared time series. Most notable is the occurrence of a statistically significant 9-day periodicity in the infrared data that is absent in the solar ultraviolet data, but is present in the time series of the Ap and Kp indexes. These results imply a coupling of the geomagnetic environment to the infrared energy budget of the thermosphere. We will also examine the energy balance above 100 km with these data.
[show abstract][hide abstract] ABSTRACT: The SOFIE instrument was launched on-board the AIM (Aeronomy of Ice in the Mesosphere) satellite on April 25, 2007. SOFIE provides measurements for the study of Polar Mesospheric Clouds (PMCs) that appear near 83km, just below the high latitude summer mesopause. The instrument has now operated nominally through the first northern hemisphere PMC season. SOFIE is designed to measure broadband transmission to extremely high precision (
[show abstract][hide abstract] ABSTRACT: The Solar Occultation For Ice Experiment (SOFIE) was launched onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite on 25 April 2007, and began science observations on 14 May 2007. SOFIE conducts solar occultation measurements in 16 spectral bands that are used to retrieval vertical profiles of temperature, O3, H2O, CO2, CH4, NO, and polar mesospheric cloud (PMC) extinction at 11 wavelengths. SOFIE provides 15 sunrise and 15 sunset measurements each day at latitudes from 65°-85°S and 65°-85°N. This work describes the SOFIE experiment and shows preliminary retrieval results based on observations from the initial months on-orbit.
[show abstract][hide abstract] ABSTRACT: Calibration performed on a new solar occultation instrument in the summer of 2005 uncovered unexpected non- linearity in signals from HgCdTe photo-conductive detectors. This led to concerns that the HALogen Occultation Experiment (HALOE) instrument on-board the Upper Atmosphere Research Satellite (UARS) may have had similar characteristics that were never realized, due to the inability to irradiate the instrument at solar flux levels in the laboratory. This paper describes the in-orbit procedure used to calibrate the non-linearity characteristics of the HALOE detectors (just weeks before the UARS mission ended) and the consequence to the HALOE retrieved products. The response non-linearity has been included in an upgraded HALOE processing algorithm and the preliminary evaluation of impact to results for all retrieved products is presented. The greatest effects are realized in the temperature and the water vapor retrievals. Changes in the retrieved water vapor were nearly zero near the tropopause, increasing with altitude to 20% or more in the mid mesosphere. Keywords: HALOE, Occultation, Detector Non-linearity
[show abstract][hide abstract] ABSTRACT: The SABER instrument on the TIMED satellite has been making continuous
observations from orbit for more than four years (starting in 2002) of
the emission attributed to nitric oxide (NO) at 5.3 micrometers. To
date, over 2.5 million profiles have been recorded for the atmospheric
limb emission extending from 400 km to the Earth's surface. We have
analyzed the extant data set and have computed the daily global power
(Watts) radiated by NO between 100 and 200 km tangent altitude. The data
exhibit large day-to-day variability with the influence of each solar
storm event being evident. In addition, there is a definite decrease in
the emitted power over the course of the four years. The annual average
power decreases by a factor of two from 2002 to 2005. This implies a
reduction in the integrated thermospheric infrared cooling rate by a
similar amount. The temporal decrease is coincident with the marked
decline of activity in the current solar cycle as indicated by the
standard solar indexes. These results are the first quantitative measure
of the influence of solar activity on the infrared radiative energy
budget of the thermosphere.
[show abstract][hide abstract] ABSTRACT: Broadband limb measurements have been used extensively for sounding the upper atmosphere, providing excellent vertical resolution and high precision of temperature and key atmospheric constituents. Emission sensors can provide daily global maps, while occultation sensors are suited to less coverage but produce sensitive and reliable trends over years and even decades. Traditionally these sensors have relied on ground calibration to ensure that spectral out-of-band (OOB) response is either negligible or accurately modeled in the operational analysis. There are indications that these unknown effects are not always negligible. Recent analyses of measurements from an occultation experiment, HALOE (HALogen Occultation Experiment), and an emission experiment, SABER (Sounding of the Atmosphere using Broadband Emission Radiometry), were performed to test the validity of the OOB ground calibration for these two instruments. The results of these studies, including simulations, and corrections are presented, along with suggested design criteria and tests for current and future sensors.
[show abstract][hide abstract] ABSTRACT: The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment was launched on December 7, 2001 into a 74.1 degree inclined, 625 km orbit onboard the TIMED satellite. The primary science goal of SABER is to achieve major advances in understanding the structure, energetics, chemistry, and dynamics in the atmospheric region extending from 60 to 180 km altitude. SABER has been operating almost continuously since activation using the space flight proven experiment approach of spectral broadband limb emission radiometry applied in 10 selected infrared spectral bands ranging from 1.27 micrometers to 17 micrometers wavelength. Observed limb emission profiles are being processed on the ground to provide vertical profiles with 2 km altitude resolution of O3, H2O, CO2, O, H, energetics parameters and temperature. Measurements are made both night and day over the latitude range from 52S to 83N with alternating hemisphere coverage every 60 days. We describe in this paper a preliminary climatology of temperature and ozone using retrieval version 1.04 and show updates using the latest V1.06 retrieval. Zonal means, polar projections, temporal variability, day/night behavior and "typical" responses to geophysical events will be described. The latter is described using NO radiance observations.
[show abstract][hide abstract] ABSTRACT: HALOE has been in operation for over 12 years providing quality data from the upper troposphere through the mesopause. Monitoring the stability of the experiment is important to ensure a consistent data set spanning such a long time period. Four calibration tests used to routinely ascertain instrument performance will be described here: gas cell concentration, gain, boresight, and field of view (FOV) mismatch. The concentrations of the species in the gas cells that are utilized in the gas correlation channels are determined by a novel approach using the retrieval results themselves. The gains between the gas cell and vacuum paths are determined by instrument scans of the solar disk and the onboard blackbody. The boresight accuracy of HALOE's telescope and the FOV mismatch function between the detectors for each gas correlation channel are determined from special solar scan data. Trends in this calibration data and their effect on final products will be presented along with techniques for determining new calibration values.
[show abstract][hide abstract] ABSTRACT: Recently, an analysis of the Halogen Occultation Experiment (HALOE) infrared solar occultation measurements confirmed for the first time the long-held belief that polar mesospheric clouds (PMCs) are composed of water-ice. Here we present an analysis of HALOE's long-term record of these clouds, covering both hemispheres and spanning nearly a complete solar cycle. Continuing since 1991, HALOE has amassed over 7,000 soundings in the polar-summer (above 50 degrees latitude and within six weeks of summer solstice), providing a unique and valuable dataset for the study of PMCs. We discuss methods for extracting spectral signatures and particle size estimates from the measurements. We examine the occurrence statistics of the clouds in both hemispheres, for sunrises and sunsets, and time during the PMC season. We also discuss an improved observational procedure that enhances the signal quality at these altitudes. With continued operations in the next few years we will be able to refine these measurements, extend the record to cover at least one complete solar cycle and obtain validation opportunities.