scholarly journals Wind field differences between three meteorological reanalysis data sets detected by evaluating atmospheric excitation of Earth rotation

2008 ◽  
Vol 113 (D7) ◽  
Author(s):  
Y. Masaki
Keyword(s):  
Earth Rotation ◽  
Wind Field ◽  
Reanalysis Data ◽  
Data Sets ◽  
Atmospheric Excitation

scholarly journals Short-Period Oscillations of Earth Rotation

2000 ◽  
Vol 178 ◽  
pp. 533-544 ◽  
Author(s):  
B. Kołaczek ◽  
W. Kosek ◽  
H. Schuh
Keyword(s):  
Seasonal Variations ◽  
Earth Rotation ◽  
Polar Motion ◽  
Correlation Coefficients ◽  
Data Sets ◽  
Annual Variations ◽  
Geodetic Vlbi ◽  
Atmospheric Excitation ◽  
Short Period ◽  
Seasonal Oscillations

AbstractSub-seasonal variations and especially sub-seasonal oscillations with periods of about 120, 60, 50, 40 days in polar motion and of about 120, 60–90, and 50 days in LOD are presented. Variations of amplitudes of these sub-seasonal oscillations of polar motion are shown. Maxima of these amplitudes are of the order of 2–4 mas. These oscillations are elliptical ones. The correlation coefficients between geodetic and atmospheric excitation functions in this range of the spectrum are variable and have annual variations. Maxima of correlation coefficients are of the order of 0.6–0.8.Modern geodetic VLBI experiments provide very accurate results in polar motion and UT1–UTC with a temporal resolution of 3–7 minutes. Several irregular, quasi-periodic variations were found. In many UT1–UTC data sets, oscillations with periods around 8 hours and between 5 and 7 hours can be seen.

scholarly journals First measurements of tides in the stratosphere and lower mesosphere by ground-based Doppler microwave wind radiometry

2020 ◽  
Vol 20 (4) ◽  
pp. 2367-2386 ◽  
Author(s):  
Jonas Hagen ◽  
Klemens Hocke ◽  
Gunter Stober ◽  
Simon Pfreundschuh ◽  
Axel Murk ◽  
...  
Keyword(s):  
Wind Field ◽  
Mean Amplitude ◽  
Reanalysis Data ◽  
Diurnal Tide ◽  
Atmospheric Tides ◽  
Data Sets ◽  
Polar Regions ◽  
Good Correspondence ◽  
Vertical Coupling ◽  
Diurnal Tides

Abstract. Atmospheric tides are important for vertical coupling in the atmosphere, from the stratosphere down to the troposphere and up to the thermosphere. They are planetary-scale gravity waves with well-known periods that are integer fractions of a day and can be observed in the temperature or wind fields in the atmosphere. Most lidar techniques and satellites measure atmospheric tides only in the temperature field and continuous measurements of the tides in the wind field of the stratosphere and lower mesosphere are rare, even though, with modern lidars, they would be feasible. In this study, we present measurements of the diurnal tide in the wind field in the stratosphere and lower mesosphere by ground-based microwave wind radiometry for two different campaigns in tropical and polar regions. Further, we compare our measurements to MERRA-2 reanalysis data. In the tri-monthly mean, we find a good correspondence in the amplitude and phase of the diurnal tide between measurements and reanalysis with the most important features of the diurnal tides represented in both data sets. When looking at shorter timescales, we find significant differences in the data sets. We make an attempt to examine these differences and discriminate between atmospheric variability and noise, and we present some hints for intermittent diurnal tides. We conclude that continuous ground-based observations of tides in the middle atmospheric wind field are feasible, and they deliver consistent results for the mean amplitude and phase of the diurnal tide in the tri-monthly mean. We further discuss the limitations in regards to short timescale observations of tides and the possibility to provide additional insight into middle atmospheric dynamics that is complementary to temperature observations and reanalysis data.

scholarly journals First measurements of tides in the stratosphere and lower mesosphere by ground-based Doppler microwave wind radiometry

2019 ◽  
Author(s):  
Jonas Hagen ◽  
Klemens Hocke ◽  
Gunter Stober ◽  
Simon Pfreundschuh ◽  
Axel Murk ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Wind Field ◽  
Reanalysis Data ◽  
Diurnal Tide ◽  
Atmospheric Tides ◽  
Data Sets ◽  
Polar Regions ◽  
Additional Insight ◽  
Vertical Coupling ◽  
Middle Atmospheric Dynamics

Abstract. Atmospheric tides are important for the vertical coupling in the atmosphere from the stratosphere down to the troposphere and up to the ionosphere. They are gravity waves with well-known periods that are integer fractions of a day and can be observed in the temperature or wind field in the atmosphere. Current lidar and satellite techniques measure atmospheric tides only in the temperature field and continuous measurements of the tides in the wind field of the stratosphere and lower mesosphere are not available. In this study, we present measurements of the diurnal tide in the wind field in the stratosphere and lower mesosphere by ground based microwave wind radiometry for two different campaigns in tropical and polar regions. Further, we compare our measurements to MERRA-2 reanalysis data. In the three-monthly mean, we find a good overall correspondence between measurements and reanalysis with the most important features of the diurnal tides represented in both data sets. When looking at shorter timescales, we find an intermittency of the diurnal tide that is not represented in the MERRA-2 reanalysis data. We conclude, that continuous ground based observations of tides in the middle atmospheric wind field are feasible, even on short timescales of 7 to 13 days, and thus provide additional insight to middle atmospheric dynamics that is complementary to temperature observations and reanalysis data.

scholarly journals Southern Hemisphere atmospheric blocking diagnostic by ECMWF and NCEP/NCAR data

2012 ◽  
Vol 27 (3) ◽  
pp. 263-271 ◽  
Author(s):  
Monica Cristina Damião Mendes ◽  
Iracema F. A. Cavalcanti ◽  
Dirceu Luis Herdies
Keyword(s):  
Atlantic Ocean ◽  
Southern Hemisphere ◽  
Geopotential Height ◽  
Seasonal Cycle ◽  
South Pacific ◽  
Reanalysis Data ◽  
Data Sets ◽  
Atmospheric Blocking ◽  
Assimilation Scheme

An assessment of blocking episodes over the Southern Hemisphere, selected from the Era-40 and NCEP/NCAR reanalysis are presented in this study. Blocking can be defined by an objective index based on two 500 hPa geopotential height meridional gradients. The seasonal cycle and preferential areas of occurrence are well reproduced by the two data sets. In both reanalysis used in this study, South Pacific and Oceania were the preferred regions for blocking occurrence, followed by the Atlantic Ocean. However the results revealed differences in frequencies of occurrences, which may be related to the choice of assimilation scheme employed to produce the reanalysis data sets. It is important to note that the ERA 40 and NCEP/NCAR reanalysis were produced using consistent models and assimilation schemes throughout the whole reanalyzed period, which are different for each set.

scholarly journals Comparison of Reanalysis Data Sets to Comprehend the Evolution of Tropical Cyclones Over North Indian Ocean

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
P. Malakar ◽  
A.P. Kesarkar ◽  
J.N. Bhate ◽  
V. Singh ◽  
A. Deshamukhya
Keyword(s):  
Indian Ocean ◽  
Tropical Cyclones ◽  
Reanalysis Data ◽  
North Indian Ocean ◽  
Data Sets

scholarly journals Asian water tower evinced in total column water vapor: a comparison among multiple satellite and reanalysis data sets

2019 ◽  
Vol 54 (1-2) ◽  
pp. 231-245 ◽  
Author(s):  
Yin Zhao ◽  
Tianjun Zhou
Keyword(s):  
Water Vapor ◽  
Satellite Data ◽  
Annual Cycle ◽  
Reanalysis Data ◽  
Radiosonde Data ◽  
Data Sets ◽  
Important Indicator ◽  
Ensemble Mean ◽  
Asian Water ◽  
Total Column

Abstract The total column water vapor (TCWV) over the Tibetan Plateau (TP) is one important indicator of the Asian water tower, and the changes in the TCWV are vital to the climate and ecosystem in downstream regions. However, the observational data is insufficient to understand the changes in the TCWV due to the high elevation of the TP. Satellite and reanalysis data can be used as substitutes, but their quality needs to be evaluated. In this study, based on a homogenized radiosonde data set, a comprehensive evaluation of the TCWV over the TP derived from two satellite data sets (AIRS-only and AIRS/AMSU) and seven existing reanalysis data sets (MERRA, MERRA2, NCEP1, NCEP2, CFSR, ERA-I, JRA55) is performed in the context of the climatology, annual cycle and interannual variability. Both satellite data sets reasonably reproduce the characteristics of the TCWV over the TP. All reanalysis data sets perform well in reproducing the annual mean climatology of the TCWV over the TP (R = 0.99), except for NCEP1 (R = 0.96) and NCEP2 (R = 0.92). ERA-I is more reliable in capturing the spatial pattern of the annual cycle (R = 0.94), while NCEP1 shows the lowest skill (R = 0.72). JRA55 performs best in capturing the features of the interannual coherent variation (EOF1, R = 0.97). The skill-weighted ensemble mean of the reanalysis data performs better than the unweighted ensemble mean and most of the single reanalysis data sets. The evaluation provides essential information on both the strengths and weaknesses of the major satellite and reanalysis data sets in measuring the total column water vapor over the TP.

Evaluation of evapotranspiration estimates from observed and reanalysis data sets over Indian region

2019 ◽  
Vol 39 (15) ◽  
pp. 5791-5800 ◽  
Author(s):  
G. Purnadurga ◽  
T.V. Lakshmi Kumar ◽  
K. Koteswara Rao ◽  
Humberto Barbosa ◽  
R.K. Mall
Keyword(s):  
Reanalysis Data ◽  
Indian Region ◽  
Data Sets

scholarly journals Surface temperature response to the major volcanic eruptions in multiple reanalysis data sets

2019 ◽  
Author(s):  
Masatomo Fujiwara ◽  
Patrick Martineau ◽  
Jonathon S. Wright
Keyword(s):  
Time Series ◽  
Surface Temperature ◽  
Volcanic Eruptions ◽  
Reanalysis Data ◽  
Data Sets ◽  
Hemispheric Differences ◽  
Quasi Biennial Oscillation ◽  
Cooling Period ◽  
El Chichón ◽  
El Chichon

Abstract. The global response of air temperature at 2 metre above the surface to the eruptions of Mount Agung in March 1963, El Chichón in April 1982, and Mount Pinatubo in June 1991 is investigated using 11 global atmospheric reanalysis data sets (JRA-55, JRA-25, MERRA-2, MERRA, ERA-Interim, ERA-40, CFSR, NCEP-NCAR R-1, 20CR version 2c, ERA-20C, and CERA-20C). Multiple linear regression (MLR) is applied to the monthly mean time series of temperature for two periods, 1980–2010 (for 10 reanalyses) and 1958–2001 (for six reanalyses), by considering explanatory factors of seasonal harmonics, linear trends, Quasi-Biennial Oscillation (QBO), solar cycle, tropical sea surface temperature (SST) variations in the Pacific, Indian, and Atlantic Oceans, and Arctic SST variations. Empirical orthogonal function (EOF) analysis is applied to these climatic indices to obtain a set of orthogonal indices to be used for the MLR. The residuals of the MLR are used to define the volcanic signals for the three eruptions separately. First, latitudinally averaged time series of the residuals are investigated and compared with the results from previous studies. Then, the geographical distribution of the response during the peak cooling period after each eruption is investigated. In general, different reanalyses show similar geographical patterns of the response, but with the largest differences in the polar regions. The Pinatubo response shows largest average cooling in the 60° N–60° S region among the three eruptions, with a peak cooling of 0.10–0.15 K. The El Chichón response shows slightly larger cooling in the NH than in the Southern Hemisphere (SH), while the Agung response shows larger cooling in the SH. These hemispheric differences are consistent with the distribution of stratospheric aerosol optical depth after these eruptions; however, the peak cooling after these two eruptions is comparable in magnitude to unexplained cooling events in other periods without volcanic influence. Other methods in which the MLR model is used with different sets of indices are also tested, and it is found that careful treatment of tropical SST variability is necessary to evaluate the surface response to volcanic eruptions in observations and reanalyses.

scholarly journals A comparison of Loon balloon observations and stratospheric reanalysis products

2017 ◽  
Vol 17 (2) ◽  
pp. 855-866 ◽  
Author(s):  
Leon S. Friedrich ◽  
Adrian J. McDonald ◽  
Gregory E. Bodeker ◽  
Kathy E. Cooper ◽  
Jared Lewis ◽  
...  
Keyword(s):  
Reanalysis Data ◽  
Location Information ◽  
Data Sets ◽  
Wind Fields ◽  
Weather Forecasts ◽  
Wind Speeds ◽  
Zonal Winds ◽  
Long Duration ◽  
Environmental Prediction ◽  
Modern Era

Abstract. Location information from long-duration super-pressure balloons flying in the Southern Hemisphere lower stratosphere during 2014 as part of X Project Loon are used to assess the quality of a number of different reanalyses including National Centers for Environmental Prediction Climate Forecast System version 2 (NCEP-CFSv2), European Centre for Medium-Range Weather Forecasts (ERA-Interim), NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA), and the recently released MERRA version 2. Balloon GPS location information is used to derive wind speeds which are then compared with values from the reanalyses interpolated to the balloon times and locations. All reanalysis data sets accurately describe the winds, with biases in zonal winds of less than 0.37 m s−1 and meridional biases of less than 0.08 m s−1. The standard deviation on the differences between Loon and reanalyses zonal winds is latitude-dependent, ranging between 2.5 and 3.5 m s−1, increasing equatorward. Comparisons between Loon trajectories and those calculated by applying a trajectory model to reanalysis wind fields show that MERRA-2 wind fields result in the most accurate simulated trajectories with a mean 5-day balloon–reanalysis trajectory separation of 621 km and median separation of 324 km showing significant improvements over MERRA version 1 and slightly outperforming ERA-Interim. The latitudinal structure of the trajectory statistics for all reanalyses displays marginally lower mean separations between 15 and 35° S than between 35 and 55° S, despite standard deviations in the wind differences increasing toward the equator. This is shown to be related to the distance travelled by the balloon playing a role in the separation statistics.

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