[1] Measurements of Pollution in the Troposphere (MOPITT) is a new remote sensing instrument aboard the Earth Observing System (EOS) ''Terra'' satellite which exploits gas correlation radiometry principles to quantify tropospheric concentrations of carbon monoxide (CO) and methane (CH 4 ). The MOPITT CO retrieval algorithm employs a nonlinear optimal estimation method to iteratively solve for the CO profile which is statistically most consistent with both the satellite-measured radiances and a priori information. The algorithm's theoretical basis is described in terms of the observed radiances and their weighting functions, the a priori information, and the retrieval averaging kernels. Examples of actual CO retrievals over scenes with contrasting pollution conditions are demonstrated, and interpreted in the context of the retrieval averaging kernels and a priori.

.[1] Validation of the Measurements of Pollution in the Troposphere (MOPITT) retrievals of carbon monoxide (CO) has been performed with a varied set of correlative data. These include in situ observations from a regular program of aircraft observations at five sites ranging from the Arctic to the tropical South Pacific Ocean. Additional in situ profiles are available from several short-term research campaigns situated over North and South America, Africa, and the North and South Pacific Oceans. These correlative measurements are a crucial component of the validation of the retrieved CO profiles and columns from MOPITT. The current validation results indicate good quantitative agreement between MOPITT and in situ profiles, with an average bias less than 20 ppbv at all levels. Comparisons with measurements that were timed to sample profiles coincident with MOPITT overpasses show much less variability in the biases than those made by various groups as part of research field experiments. The validation results vary somewhat with location, as well as a change in the bias between the Phase 1 and Phase 2 retrievals (before and after a change in the instrument configuration due to a cooler failure). During Phase 1, a positive bias is found in the lower troposphere at cleaner locations, such as over the Pacific Ocean, with smaller biases at continental sites. However, the Phase 2 CO retrievals show a negative bias at the Pacific Ocean sites. These validation comparisons provide critical assessments of the retrievals and will be used, in conjunction with ongoing improvements to the retrieval algorithms, to further reduce the retrieval biases in future data versions.

This paper presents results of the inverse modeling of carbon monoxide surface sources on a monthly and regional basis using the MOPITT (Measurement Of the Pollution In The Troposphere) CO retrievals. The targeted time period is from April 2000 to March 2001. A sequential and time-dependent inversion scheme is implemented to correct an a priori set of monthly mean CO sources. The a posteriori estimates for the total anthropogenic (fossil fuel + biofuel + biomass burning) surface sources of CO in TgCO/yr are 509 in Asia, 267 in Africa, 140 in North America, 90 in Europe and 84 in Central and South America. Inverting on a monthly scale allows one to assess a corrected seasonality specific to each source type and each region. Forward CTM simulations with the a posteriori emissions show a substantial improvement of the agreement between modeled CO and independent in situ observation

[1] Deep intrusions of tropospheric air into the lower stratosphere above the subtropical jet are investigated using new observations and meteorological analyses. These intrusions are characterized by low ozone concentration and low static stability. The low-ozone layer is consistently observed from ozonesonde profiles and satellite remote sensing data from Aura/HIRDLS. The intruding layer occurs along and under the poleward extending tropical tropopause, which becomes the secondary tropopause in middle to high latitudes. The association of the ozone and the thermal structure provides evidence for the physical significance of the subtropical tropopause break and the secondary tropopause. The core of the intruding layer is typically between 370 and 400 K potential temperature ($15 km), but the vertical extent of the intrusion can impact ozone above 400 K, the lower boundary of the overworld. Two intrusion events over the continental United States in the spring of 2007 are analyzed to show the spatial extent and the temporal evolution of the intruding air mass. These examples demonstrate the effectiveness of potential temperature lapse rate, i.e., static stability, as a diagnostic for the intrusion event.Comparison with the potential vorticity field is made to show the complementarity of the two dynamical fields. The static stability diagnostic provides a tool to map out the horizontal extent of the intruding layer and to investigate its evolution. Furthermore, the diagnostic makes it possible to forecast the intrusion event for field studies.

[1] A three-dimensional (3-D) inverse modeling scheme is used to constrain the direct surface emissions of carbon monoxide CO. A priori estimates of CO emissions are taken from various inventories and are included in the IMAGES model to compute the distribution of CO. The modeled CO mixing ratios are compared with observations at 39 CMDL stations, averaged over the years [1990][1991][1992][1993][1994][1995][1996]. The interannual variability of CO sources is therefore ignored. We show that the method used (time-dependent synthesis inversion) is able to adjust the surface fluxes on a monthly basis in order to improve the agreement between the observed and the modeled CO mixing ratios at the stations. The Earth surface is divided into regions. The spatial distribution of CO sources is fixed inside each of these regions. The inversion scheme optimizes the intensities of the emissions fluxes for the following processes: technological activities, forest and savanna burning, agricultural waste burning and fuelwood use, soil/vegetation emissions, and oceanic emissions. The inversion significantly reduces the uncertainties on the surface sources over Europe, North America and Asia. The most striking result is the increase (almost by a factor of 2) of CO flux from Asia in all a posteriori scenarios. The uncertainties on the Southern Hemisphere emissions remain large after the inversion, because the current observational surface network is too sparse at these latitudes. The inversion, moreover, shifts the peak in biomass burning emissions in the Southern Hemisphere by one month. This temporal shift ensures a better match of the observed and modeled CO seasonal cycle at the Ascension Island station. We also attempted to optimize the annual and global productions of CO due to methane and NMHC. With the current set of data, the scheme was not able to differentiate between these two sources, and hence only the total chemical production of CO can be optimized.

During stratospheric sudden warming (SSW) periods large changes in the low‐latitude vertical drift have been observed at Jicamarca as well as in other longitudinal sectors. In general, a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed. During the January 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed. At Jicamarca the previously reported SSW behavior prevails; however, no shift of the daytime maximum drift was exhibited in the African sector. Using the National Center for Atmospheric Research thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model (TIME‐GCM) the possible causes for the longitudinal difference are examined. The timing of the strong SSW effect in the vertical drift (15–20 January) coincides with moderate geomagnetic activity. The simulation indicates that approximately half of the daytime vertical drift increase in the American sector may be related to the moderate geophysical conditions (Kp = 4) with the effect being negligible in the African sector. The simulation suggests that the wind dynamo accounts for approximately 50% of the daytime vertical drift in the American sector and almost 100% in the African sector. The simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 (SW1) mainly contribute to the daytime wind dynamo and vertical drift. Numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence (absence) of a local time shift in the daytime maximum drift in the American (African) sector.

Ionospheric day‐to‐day variability is a ubiquitous feature, even in the absence of appreciable geomagnetic activities. Although meteorological perturbations have been recognized as an important source of the variability, it is not well represented in previous modeling studies and the mechanism is not well understood. This study demonstrates that the thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (TIME‐GCM) constrained in the stratosphere and mesosphere by the hourly whole atmosphere community climate model (WACCM) simulations is capable of reproducing observed features of day‐to‐day variability in the thermosphere‐ionosphere. Realistic weather patterns in the lower atmosphere in WACCM were specified by Modern Era Retrospective Reanalysis for Research and Application (MERRA). The day‐to‐day variations in mean zonal wind, migrating and nonmigrating tides in the thermosphere, vertical and zonal E × B drifts, and ionosphere F2 layer peak electron density (NmF2) are examined. The standard deviations of the drifts and NmF2 show local time and longitudinal dependence that compare favorably with observations. Their magnitudes are 50% or more of those from observations. The day‐to‐day thermosphere and ionosphere variability in the model is primarily caused by the perturbations originated in lower atmosphere, since the model simulation is under constant solar minimum and low geomagnetic conditions.

Nitrate ion spikes in polar ice cores are contentiously used to estimate the intensity, frequency, and probability of historical solar proton events, quantities that are needed to prepare for potentially society‐crippling space weather events. We use the Whole Atmosphere Community Climate Model to calculate how large an event would have to be to produce enough odd nitrogen throughout the atmosphere to be discernible as nitrate peaks at the Earth's surface. These hypothetically large events are compared with probability of occurrence estimates derived from measured events, sunspot records, and cosmogenic radionuclides archives. We conclude that the fluence and spectrum of solar proton events necessary to produce odd nitrogen enhancements equivalent to the spikes of nitrate ions in Greenland ice cores are unlikely to have occurred throughout the Holocene, confirming that nitrate ions in ice cores are not suitable proxies for historical individual solar proton events.