W. H. Daffer
California Institute of Technology
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Featured researches published by W. H. Daffer.
Geophysical Research Letters | 2009
G. L. Manney; Michael J. Schwartz; Kirstin Krüger; Michelle L. Santee; Steven Pawson; Jae N. Lee; W. H. Daffer; R. Fuller; Nathaniel J. Livesey
A major stratospheric sudden warming (SSW) in January 2009 was the strongest and most prolonged on record. Aura Microwave Limb Sounder (MLS) observations are used to provide an overview of dynamics and transport during the 2009 SSW, and to compare with the intense, long-lasting SSW in January 2006. The Arctic polar vortex split during the 2009 SSW, whereas the 2006 SSW was a vortex displacement event. Winds reversed to easterly more rapidly and reverted to westerly more slowly in 2009 than in 2006. More mixing of trace gases out of the vortex during the decay of the vortex fragments, and less before the fulfillment of major SSW criteria, was seen in 2009 than in 2006; persistent well-defined fragments of vortex and anticyclone air were more prevalent in 2009. The 2009 SSW had a more profound impact on the lower stratosphere than any previously observed SSW, with no significant recovery of the vortex in that region. The stratopause breakdown and subsequent reformation at very high altitude, accompanied by enhanced descent into a rapidly strengthening upper stratospheric vortex, were similar in 2009 and 2006. Many differences between 2006 and 2009 appear to be related to the different character of the SSWs in the two years.
Journal of Geophysical Research | 2007
Alyn Lambert; William G. Read; Nathaniel J. Livesey; Michelle L. Santee; G. L. Manney; L. Froidevaux; Dong L. Wu; Michael J. Schwartz; Hugh C. Pumphrey; Carlos Jiménez; Gerald E. Nedoluha; R. E. Cofield; D. T. Cuddy; W. H. Daffer; Brian J. Drouin; R. Fuller; R. F. Jarnot; B. W. Knosp; Herbert M. Pickett; V. S. Perun; W. V. Snyder; P. C. Stek; R. P. Thurstans; Paul A. Wagner; J. W. Waters; Kenneth W. Jucks; G. C. Toon; R. A. Stachnik; Peter F. Bernath; C. D. Boone
[1] The quality of the version 2.2 (v2.2) middle atmosphere water vapor and nitrous oxide measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System (EOS) Aura satellite is assessed. The impacts of the various sources of systematic error are estimated by a comprehensive set of retrieval simulations. Comparisons with correlative data sets from ground-based, balloon and satellite platforms operating in the UV/visible, infrared and microwave regions of the spectrum are performed. Precision estimates are also validated, and recommendations are given on the data usage. The v2.2 H2O data have been improved over v1.5 by providing higher vertical resolution in the lower stratosphere and better precision above the stratopause. The single-profile precision is � 0.2–0.3 ppmv (4–9%), and the vertical resolution is � 3–4 km in the stratosphere. The precision and vertical resolution become worse with increasing height above the stratopause. Over the pressure range 0.1–0.01 hPa the precision degrades from 0.4 to 1.1 ppmv (6–34%), and the vertical resolution degrades to � 12–16 km. The accuracy is estimated to be 0.2–0.5 ppmv (4–11%) for the pressure range 68–0.01 hPa. The scientifically useful range of the H2O data is from 316 to 0.002 hPa, although only the 82–0.002 hPa pressure range is validated here. Substantial improvement has been achieved in the v2.2 N2O data over v1.5 by reducing a significant low bias in the stratosphere and eliminating unrealistically high biased mixing ratios in the polar regions. The single-profile precision is � 13–25 ppbv (7–38%), the vertical resolution is � 4–6 km and the accuracy is estimated to be 3–70 ppbv (9–25%) for the pressure range 100–4.6 hPa. The scientifically useful range of the N2O data is from 100 to 1 hPa.
Journal of Geophysical Research | 2008
L. Froidevaux; Yibo Jiang; Alyn Lambert; Nathaniel J. Livesey; William G. Read; J. W. Waters; Edward V. Browell; J. W. Hair; M. Avery; T. J. McGee; Laurence Twigg; G. K. Sumnicht; K. W. Jucks; J. J. Margitan; B. Sen; R. A. Stachnik; G. C. Toon; Peter F. Bernath; C. D. Boone; Kaley A. Walker; Mark J. Filipiak; R. S. Harwood; R. Fuller; G. L. Manney; Michael J. Schwartz; W. H. Daffer; Brian J. Drouin; R. E. Cofield; D. T. Cuddy; R. F. Jarnot
[1] The Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura satellite has provided essentially daily global measurements of ozone (O3) profiles from the upper troposphere to the upper mesosphere since August of 2004. This paper focuses on validation of the MLS stratospheric standard ozone product and its uncertainties, as obtained from the 240 GHz radiometer measurements, with a few results concerning mesospheric ozone. We compare average differences and scatter from matched MLS version 2.2 profiles and coincident ozone profiles from other satellite instruments, as well as from aircraft lidar measurements taken during Aura Validation Experiment (AVE) campaigns. Ozone comparisons are also made between MLS and balloon-borne remote and in situ sensors. We provide a detailed characterization of random and systematic uncertainties for MLS ozone. We typically find better agreement in the comparisons using MLS version 2.2 ozone than the version 1.5 data. The agreement and the MLS uncertainty estimates in the stratosphere are often of the order of 5%, with values closer to 10% (and occasionally 20%) at the lowest stratospheric altitudes, where small positive MLS biases can be found. There is very good agreement in the latitudinal distributions obtained from MLS and from coincident profiles from other satellite instruments, as well as from aircraft lidar data along the MLS track.
Journal of Geophysical Research | 2008
G. L. Manney; Kirstin Krüger; Steven Pawson; Ken Minschwaner; Michael J. Schwartz; W. H. Daffer; Nathaniel J. Livesey; Martin G. Mlynczak; Ellis E. Remsberg; James M. Russell; J. W. Waters
Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data provide the first opportunity to characterize the four-dimensional stratopause evolution throughout the life-cycle of a major stratospheric sudden warming (SSW). The polar stratopause, usually higher than that at midlatitudes, dropped by ∼30 km and warmed during development of a major “wave 1” SSW in January 2006, with accompanying mesospheric cooling. When the polar vortex broke down, the stratopause cooled and became ill-defined, with a nearly isothermal stratosphere. After the polar vortex started to recover in the upper stratosphere/lower mesosphere (USLM), a cool stratopause reformed above 75 km, then dropped and warmed; both the mesosphere above and the stratosphere below cooled at this time. The polar stratopause remained separated from that at midlatitudes across the core of the polar night jet. In the early stages of the SSW, the strongly tilted (westward with increasing altitude) polar vortex extended into the mesosphere, and enclosed a secondary temperature maximum extending westward and slightly equatorward from the highest altitude part of the polar stratopause over the cool stratopause near the vortex edge. The temperature evolution in the USLM resulted in strongly enhanced radiative cooling in the mesosphere during the recovery from the SSW, but significantly reduced radiative cooling in the upper stratosphere. Assimilated meteorological analyses from the European Centre for Medium-Range weather Forecasts (ECMWF) and Goddard Earth Observing System Version 5.0.1 (GEOS-5), which are not constrained by data at polar stratopause altitudes and have model tops near 80 km, could not capture the secondary temperature maximum or the high stratopause after the SSW; they also misrepresent polar temperature structure during and after the stratopause breakdown, leading to large biases in their radiative heating rates. ECMWF analyses represent the stratospheric temperature structure more accurately, suggesting a better representation of vertical motion; GEOS-5 analyses more faithfully describe stratopause level wind and wave amplitudes. The high-quality satellite temperature data used here provide the first daily, global, multiannual data sets suitable for assessing and, eventually, improving representation of the USLM in models and assimilation systems.
Journal of Geophysical Research | 2007
Michelle L. Santee; Alyn Lambert; William G. Read; Nathaniel J. Livesey; G. L. Manney; R. E. Cofield; D. T. Cuddy; W. H. Daffer; Brian J. Drouin; L. Froidevaux; R. Fuller; R. F. Jarnot; B. W. Knosp; V. S. Perun; W. V. Snyder; P. C. Stek; R. P. Thurstans; Paul A. Wagner; J. W. Waters; Brian J. Connor; Jakub Urban; Donal P. Murtagh; Philippe Ricaud; B. Barret; Armin Kleinböhl; Jayanarayanan Kuttippurath; H. Küllmann; M. von Hobe; G. C. Toon; R. A. Stachnik
We assess the quality of the version 2.2 (v2.2) ClO measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS v2.2 ClO data are scientifically useful over the range 100 to 1 hPa, with a single- profile precision of similar to 0.1 ppbv throughout most of the vertical domain. Vertical resolution is similar to 3-4 km. Comparisons with climatology and correlative measurements from a variety of different platforms indicate that both the amplitude and the altitude of the peak in the ClO profile in the upper stratosphere are well determined by MLS. The latitudinal and seasonal variations in the ClO distribution in the lower stratosphere are also well determined, but a substantial negative bias is present in both daytime and nighttime mixing ratios at retrieval levels below (i. e., pressures larger than) 22 hPa. Outside of the winter polar vortices, this negative bias can be eliminated by subtracting gridded or zonal mean nighttime values from the individual daytime measurements. In studies for which knowledge of lower stratospheric ClO mixing ratios inside the winter polar vortices to better than a few tenths of a ppbv is needed, however, day - night differences are not recommended and the negative bias must be corrected for by subtracting the estimated value of the bias from the individual measurements at each affected retrieval level.
Journal of Geophysical Research | 2007
Yibo Jiang; L. Froidevaux; Alyn Lambert; Nathaniel J. Livesey; William G. Read; J. W. Waters; Bojan Bojkov; Thierry Leblanc; I. S. McDermid; Sophie Godin-Beekmann; Mark J. Filipiak; R. S. Harwood; R. Fuller; W. H. Daffer; Brian J. Drouin; R. E. Cofield; D. T. Cuddy; R. F. Jarnot; B. W. Knosp; V. S. Perun; Michael J. Schwartz; W. V. Snyder; P. C. Stek; R. P. Thurstans; P. A. Wagner; M. Allaart; S. B. Andersen; G. E. Bodeker; B. Calpini; H. Claude
We present validation studies of MLS version 2.2 upper tropospheric and stratospheric ozone profiles using ozonesonde and lidar data as well as climatological data. Ozone measurements from over 60 ozonesonde stations worldwide and three lidar stations are compared with coincident MLS data. The MLS ozone stratospheric data between 150 and 3 hPa agree well with ozonesonde measurements, within 8% for the global average. MLS values at 215 hPa are biased high compared to ozonesondes by A`20% at middle to high latitude, although there is a lot of variability in this altitude region. Comparisons between MLS and ground-based lidar measurements from Mauna Loa, Hawaii, from the Table Mountain Facility, California, and from the Observatoire de Haute-Provence, France, give very good agreement, within A`5%, for the stratospheric values. The comparisons between MLS and the Table Mountain Facility tropospheric ozone lidar show that MLS data are biased high by A`30% at 215 hPa, consistent with that indicated by the ozonesonde data. We obtain better global average agreement between MLS and ozonesonde partial column values down to 215 hPa, although the average MLS values at low to middle latitudes are higher than the ozonesonde values by up to a few percent. MLS v2.2 ozone data agree better than the MLS v1.5 data with ozonesonde and lidar measurements. MLS tropical data show the wave one longitudinal pattern in the upper troposphere, with similarities to the average distribution from ozonesondes. High upper tropospheric ozone values are also observed by MLS in the tropical Pacific from June to November.
Journal of Climate | 2014
G. L. Manney; M. I. Hegglin; W. H. Daffer; Michael J. Schwartz; Michelle L. Santee; Steven Pawson
AbstractA global climatology (1979–2012) from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) shows distributions and seasonal evolution of upper tropospheric jets and their relationships to the stratospheric subvortex and multiple tropopauses. The overall climatological patterns of upper tropospheric jets confirm those seen in previous studies, indicating accurate representation of jet stream dynamics in MERRA. The analysis shows a Northern Hemisphere (NH) upper tropospheric jet stretching nearly zonally from the mid-Atlantic across Africa and Asia. In winter–spring, this jet splits over the eastern Pacific, merges again over eastern North America, and then shifts poleward over the North Atlantic. The jets associated with tropical circulations are also captured, with upper tropospheric westerlies demarking cyclonic flow downstream from the Australian and Asian monsoon anticyclones and associated easterly jets. Multiple tropopauses associated with the thermal tropopause “break”...
Journal of Geophysical Research | 2015
Michael J. Schwartz; G. L. Manney; M. I. Hegglin; Nathaniel J. Livesey; Michelle L. Santee; W. H. Daffer
Upper tropospheric and lower stratospheric measurements from the Aura Microwave Limb Sounder (MLS), the Aura High Resolution Dynamics Limb Sounder (HIRDLS), and the Atmospheric Chemistry Experiment-Fourier transform spectrometer (ACE-FTS) are used to present the first global climatological comparison of extratropical, nonpolar trace gas distributions in double-tropopause (DT) and single-tropopause (ST) regions. Stratospheric tracers, O3, HNO3, and HCl, have lower mixing ratios ∼2–8 km above the primary (lowermost) tropopause in DT than in ST regions in all seasons, with maximum Northern Hemisphere (NH) differences near 50% in winter and 30% in summer. Southern Hemisphere winter differences are somewhat smaller, but summer differences are similar in the two hemispheres. H2O in DT regions of both hemispheres shows strong negative anomalies in November through February and positive anomalies in July through October, reflecting the strong seasonal cycle in H2O near the tropical tropopause. CO and other tropospheric tracers examined have higher DT than ST values 2–7 km above the primary tropopause, with the largest differences in winter. Large DT-ST differences extend to high NH latitudes in fall and winter, with longitudinal maxima in regions associated with enhanced wave activity and subtropical jet variations. Results for O3 and HNO3 agree closely between MLS and HIRDLS, and differences from ACE-FTS are consistent with its sparse and irregular midlatitude sampling. Consistent signatures in climatological trace gas fields provide strong evidence that transport from the tropical upper troposphere into the layer between double tropopauses is an important pathway for stratosphere-troposphere exchange.
Imaging and Applied Optics (2011), paper FMC2 | 2011
Rodica Lindenmaier; R. L. Batchelor; Kimberly Strong; S. Beagley; Richard Ménard; A. I. Jonsson; Michael Neish; Simon Chabrillat; M. P. Chipperfield; G. L. Manney; W. H. Daffer; Saroja Polavarapu; Theodore G. Shepherd; Peter F. Bernath; Kaley A. Walker
Reactive nitrogen species, NOy, play an important role in stratospheric chemistry. Using a Bruker 125HR FTIR installed at Eureka, Nunavut, ACE-FTS satellite data, and model simulations, we study the NOy budget for this Arctic site.
Journal of Geophysical Research | 2008
Michael J. Schwartz; Alyn Lambert; G. L. Manney; William G. Read; Nathaniel J. Livesey; L. Froidevaux; Chi O. Ao; Peter F. Bernath; C. D. Boone; R. E. Cofield; W. H. Daffer; Brian J. Drouin; Eric J. Fetzer; R. Fuller; R. F. Jarnot; J. H. Jiang; Yibo Jiang; B. W. Knosp; Kirstin Krüger; Jui-Lin Li; M. G. Mlynczak; Steven Pawson; James M. Russell; Michelle L. Santee; W. V. Snyder; P. C. Stek; R. P. Thurstans; Adrian M. Tompkins; Paul A. Wagner; Kaley A. Walker