Lesley Smith

Estimates of the Global Water Budget and Its Annual Cycle Using Observational and Model Data

Abstract A brief review is given of research in the Climate Analysis Section at NCAR on the water cycle. Results are used to provide a new estimate of the global hydrological cycle for long-term annual means that includes estimates of the main reservoirs of water as well as the flows of water among them. For precipitation P over land a comparison among three datasets enables uncertainties to be estimated. In addition, results are presented for the mean annual cycle of the atmospheric hydrological cycle based on 1979–2000 data. These include monthly estimates of P, evapotranspiration E, atmospheric moisture convergence over land, and changes in atmospheric storage, for the major continental landmasses, zonal means over land, hemispheric land means, and global land means. The evapotranspiration is computed from the Community Land Model run with realistic atmospheric forcings, including precipitation that is constrained by observations for monthly means but with high-frequency information taken from atmosphe...

The Mass of the Atmosphere: A Constraint on Global Analyses

Abstract The total mass of the atmosphere varies mainly from changes in water vapor loading; the former is proportional to global mean surface pressure and the water vapor component is computed directly from specific humidity and precipitable water using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analyses (ERA-40). Their difference, the mass of the dry atmosphere, is estimated to be constant for the equivalent surface pressure to within 0.01 hPa based on changes in atmospheric composition. Global reanalyses satisfy this constraint for monthly means for 1979–2001 with a standard deviation of 0.065 hPa. New estimates of the total mass of the atmosphere and its dry component, and their corresponding surface pressures, are larger than previous estimates owing to new topography of the earth’s surface that is 5.5 m lower for the global mean. Global mean total surface pressure is 985.50 hPa, 0.9 hPa higher than previous best estimates. The total mean mass of the atmosphere is 5.1480 ...

The Vertical Structure of Temperature in the Tropics: Different Flavors of El Niño

To explore the vertical coherence of the vertical temperature structure in the atmosphere, an analysis is performed of the full three-dimensional spatial structure of the temperature field monthly mean anomalies from the 40-yr ECMWF Re-Analysis (ERA-40) for a core region of the Tropics from 30°N to 30°S, with results projected globally. The focus is on the first three empirical orthogonal functions (EOFs), two of which have primary relationships to El Nino–Southern Oscillation (ENSO) and feature rather different vertical structures. The second (EOF-2) also has a weak ENSO signature but a very complex vertical structure and reflects mainly nonlinear trends, some real but also some in large part spurious and associated with problems in assimilating satellite data. The dominant pattern (EOF-1) in its positive sign features highly coherent zonal mean warming throughout the tropical troposphere from 30°N to 30°S that increases in magnitude with height to 300 hPa, drops to zero about 100 hPa at the tropopause, and has reverse sign to 30 hPa with peak negative values at 70 hPa. Spatially at low levels it shows warmth throughout most of the Tropics although with weak or slightly opposite sign in the western tropical Pacific and a strong reversed sign in the Pacific subtropics. Coherent wave structures below 700 hPa at higher latitudes cancel out in the zonal mean. However, the structure becomes more zonal above about 700 hPa and features off-equatorial maxima straddling the equator in the eastern Pacific in the upper troposphere with opposite sign at 100 hPa, as a signature of a forced Rossby wave. The corresponding sea level pressure pattern is similar to but more focused in equatorial regions than the Southern Oscillation pattern. The time series highlights the 1997/98 El Nino along with those in 1982/83 and 1986/87, and the 1988/89 La Nina, and correlates strongly with global mean surface temperatures. Missing, however, is the prolonged sequence of three successive El Nino events in the early 1990s, which are highlighted in EOF-3 as part of a mainly lower-frequency decadal variation that features modest zonal mean warming below 700 hPa, cooling from 700 to 300 hPa, and warming above 300 hPa, peaking at 100 hPa and extending from 40°N to 50°S. Spatially at the surface this pattern is dominated by Southern Oscillation wave-1 structures throughout the Tropics and especially the subtropics. The regional temperature structures are coherent throughout the troposphere, with strongest values in the Pacific and extending well into the extratropics, with a sign reversal at and above 100 hPa. Strong Rossby wave signatures are featured in the troposphere with a distinctive quadrupole pattern that reverses at 100 hPa. The vertical coherence of all patterns suggests that they should be apparent in broad-layer satellite temperature records but that stratospheric anomalies are not independent. The quite different three-dimensional structure of these different patterns highlights the need to consider the full structure outside of the Pacific and at all vertical levels in accounting for impacts of ENSO, and how they relate to the global mean.

Interannual Variability of Patterns of Atmospheric Mass Distribution

Abstract Using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) for 1958 to 2001, adjusted for bias over the southern oceans prior to 1979, an analysis is made of global patterns of monthly mean anomalies of atmospheric mass, which is approximately conserved globally. It differs from previous analyses of atmospheric circulation by effectively area weighting surface or sea level pressure that diminishes the role of high latitudes. To examine whether global patterns of behavior exist requires analysis of all seasons together (as opposite seasons occur in each hemisphere). Empirical orthogonal function (EOF) analysis, R-mode varimax-rotated EOF analysis, and cyclostationary EOF (CSEOF) analysis tools are used to explore patterns and variability on interannual and longer time scales. Clarification is given of varimax terminology and procedures that have been previously misinterpreted. The dominant global monthly variability overall is associated with the Southern Hemis...

Variations in the three-dimensional structure of the atmospheric circulation with different flavors of El Niño.

Abstract Two rather different flavors of El Nino are revealed when the full three-dimensional spatial structure of the temperature field and atmospheric circulation monthly mean anomalies is analyzed using the Japanese Reanalysis (JRA-25) temperatures from 1979 through 2004 for a core region of the tropics from 30°N to 30°S, with results projected globally onto various other fields. The first two empirical orthogonal functions (EOFs) both have primary relationships to El Nino–Southern Oscillation (ENSO) but feature rather different vertical and spatial structures. By construction the two patterns are orthogonal, but their signatures in sea level pressure, precipitation, outgoing longwave radiation (OLR), and tropospheric diabatic heating are quite similar. Moreover, they are significantly related, with EOF-2 leading EOF-1 by about 4–6 months, indicating that they play complementary roles in the evolution of ENSO events, and with each mode playing greater or lesser roles in different events and seasons. Th...

SPARC Data Initiative: A comparison of ozone climatologies from international satellite limb sounders

A comprehensive quality assessment of the ozone products from 18 limb-viewing satellite instruments is provided by means of a detailed intercomparison. The ozone climatologies in form of monthly zonal mean time series covering the upper troposphere to lower mesosphere are obtained from LIMS, SAGE I/II/III, UARS-MLS, HALOE, POAM II/III, SMR, OSIRIS, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, and SMILES within 1978–2010. The intercomparisons focus on mean biases of annual zonal mean fields, interannual variability, and seasonal cycles. Additionally, the physical consistency of the data is tested through diagnostics of the quasi-biennial oscillation and Antarctic ozone hole. The comprehensive evaluations reveal that the uncertainty in our knowledge of the atmospheric ozone mean state is smallest in the tropical and midlatitude middle stratosphere with a 1σ multi-instrument spread of less than ±5%. While the overall agreement among the climatological data sets is very good for large parts of the stratosphere, individual discrepancies have been identified, including unrealistic month-to-month fluctuations, large biases in particular atmospheric regions, or inconsistencies in the seasonal cycle. Notable differences between the data sets exist in the tropical lower stratosphere (with a spread of ±30%) and at high latitudes (±15%). In particular, large relative differences are identified in the Antarctic during the time of the ozone hole, with a spread between the monthly zonal mean fields of ±50%. The evaluations provide guidance on what data sets are the most reliable for applications such as studies of ozone variability, model-measurement comparisons, detection of long-term trends, and data-merging activities.

The SPARC Data Initiative: A comparison of ozone climatologies from international satellite limb sounders

A comprehensive quality assessment of the ozone products from 18 limb-viewing satellite instruments is provided by means of a detailed intercomparison. The ozone climatologies in form of monthly zonal mean time series covering the upper troposphere to lower mesosphere are obtained from LIMS, SAGE I/II/III, UARS-MLS, HALOE, POAM II/III, SMR, OSIRIS, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, and SMILES within 1978–2010. The intercomparisons focus on mean biases of annual zonal mean fields, interannual variability, and seasonal cycles. Additionally, the physical consistency of the data is tested through diagnostics of the quasi-biennial oscillation and Antarctic ozone hole. The comprehensive evaluations reveal that the uncertainty in our knowledge of the atmospheric ozone mean state is smallest in the tropical and midlatitude middle stratosphere with a 1σ multi-instrument spread of less than ±5%. While the overall agreement among the climatological data sets is very good for large parts of the stratosphere, individual discrepancies have been identified, including unrealistic month-to-month fluctuations, large biases in particular atmospheric regions, or inconsistencies in the seasonal cycle. Notable differences between the data sets exist in the tropical lower stratosphere (with a spread of ±30%) and at high latitudes (±15%). In particular, large relative differences are identified in the Antarctic during the time of the ozone hole, with a spread between the monthly zonal mean fields of ±50%. The evaluations provide guidance on what data sets are the most reliable for applications such as studies of ozone variability, model-measurement comparisons, detection of long-term trends, and data-merging activities.

Final correction algorithms for HIRDLS version 7 data

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument is a 21-channel limb scanning infrared radiometer, designed to make global measurements of temperature, ozone, water vapor, eight other gases and aerosols from 8 to as high as 80 km. with 1 km. vertical resolution. During launch on NASA’S Aura satellite a piece of interior lining material became lodged in the foreoptics, reducing the effective aperture by 80-95%, and inserting another signal into the system. The HIRDLS team has worked for several years to develop corrections for these effects, and recover as many as possible of the planned capabilities. This talk describes the last and probably final set of algorithms to recover the planned species. Early work developed corrections for channels with large radiances allowing temperature and ozone to be retrieved. Subsequent work has concentrated on refining these to allow species such as nitric acid, chlorofluorocarbons 11 & 12, nitrogen dioxide, N2O5, chlorine nitrate, nitrous oxide and water vapor to be recovered. Effort has gone into studying, then parameterizing in an adaptive way, the quasi-regular way the signal from the blockage varies with time during an orbit and during the mission. Several recent improvements are described. Results of these corrections show improvements in the retrieved products.

Advancing Science and Services during the 2015-16 El Niño: The NOAA El Niño Rapid Response Field Campaign

AbstractForecasts by mid-2015 for a strong El Nino during winter 2015/16 presented an exceptional scientific opportunity to accelerate advances in understanding and predictions of an extreme climat...

Diagnosing Human-Induced Dynamic and Thermodynamic Drivers of Extreme Rainfall

AbstractFactors responsible for extreme monthly rainfall over Texas/Oklahoma during May 2015 are assessed. The event had a return period of at least 400 years, compared to the prior record which was roughly a 100-year event. The event challenges attribution science to disentangle factors because it occurred during a strong El Nino, a natural pattern of variability that affects the region’s springtime rains, and during the warmest global mean temperatures since 1880. Effects of each factor are diagnosed, as is the interplay between El Nino dynamics and human-induced climate change.Analysis of historical climate simulations reveals El Nino was a necessary condition for monthly rains to occur having the severity of May 2015. Our model results further reveal that a 2015 magnitude event, whether conditioned on El Nino or not, was made neither more intense nor more likely due to human-induced climate change over the past century.The intensity of extreme May rainfall over Texas/Oklahoma, analogous to the 2015 ev...