• Journal of the Korean earth science society
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• v.21 no.5
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• pp.525-540
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• 2000

Global temperature trends of middle and upper tropospheres have been investigated using the data of satellite-observed Microwave Sounding Unit (MSU) channels 2-3(Ch2, Ch3) during the period of 1980-97 and three GCM (NCEP, ECMWF, GEOS) reanalyses during 1981-93. The global, hemispheric and tropical anomalies, computed from the data during the common period, have been intercompared in the following regions; ocean, land, and both ocean and land. The correlation with MSU in midtropospheric temperatures is the best (r=0.81${\sim}$0.95) in ECMWF, particularly over the tropics. The correlations in upper troposphere are lower (r=0.06${\sim}$0.34) due to poor quality of MSU Ch3 data consistent with previous result. The midtropospheric trends during 1981-93, obtained from MSU and three GCMs, show the global warming of 0.01${\sim}$0.18K decade$^{-1}$. The warmest years have been 1987 and 1991 in El Ni${\tilde{n}$o while the coolest 1993 and 1994 in La Ni${\tilde{n}$a. The warming (0.12${\sim}$0.13K decade$^{-1}$) in MSU over global ocean is similar to that over global land. The largest discrepancy in upper troposphere between MSU and GCMs has been found in the transition period (1984. 12-1985. 1) from NOAA 9 to 10, because of a sizable error in the MSU Ch3. The midtropospheric trends near the Korean peninsula during 1981-93 are almost negligible(-0.02K decade$^{-1}$) in MSU, but indicate significant warming (0.25-0.43K decade$^{-1}$) in GCMs. The trends are crosschecked and discussed with other two independent MSU data of Spencer and Christy (1992a, 1992b).

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.503-524
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• 2000

Intercomparisons between four kinds of data have been done to estimate the accuracy of satellite observations and model reanalysis for middle and lower tropospheric thermal state over regional oceans. The data include the Microwave Sounding Units (MSU) Channel 2 (Ch2) brightness temperatures of NOAA satellites and the vertically weighted corresponding temperature of ECMWF GCM (1980-93). The satellite data for midtropospheric temperatures are MSU2 (1980-98) in nadir direction and SC2 (1980-97) in multiple scans, and for lower tropospheric temperature SC2R (1980-97). MSU2 was derived in this study while SC2 and SC2R were described in Spencer and Christy (1992a, 1992b). Temporal correlations between the above data were high (r${\ge}$0.90) in the middle and high latitudes, but low(r${\sim}$0.65) over the low latitude and more convective regions. Their values with SC2R which included the noises due to hydrometeors and surface emission were conspicuously low. The reanalysis shows higher correlation with SC2 than with MSU2 partially because of the hydrometeors screening. SC2R in monthly climatological anomalies was more sensitive to surface thermal condition in northern hemisphere than MSU2 or SC2. The first EOF mode for the monthly mean data of MSU and ECMWF shows annual cycle over most regions except the tropics. The mode in MSU2 over the Pacific suggests the east-west dipole due to the Walker circulation, but this tendency is not clear in other data. In the first and second modes for the Ch2 anomalies over most regions, the MSU and ECMWF data commonly indicate interannual variability due to El Ni${\tilde{n}$o and La Ni${\tilde{n}$a. The substantial disagreement between observations and model reanalysis occurs over the equatorial upwelling region of the western Pacific, suggesting uncertainties in the model parameterization of atmosphere-ocean interaction.

• Journal of the Korean earth science society
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• v.22 no.5
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• pp.388-404
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• 2001

In order to examine the relative accuracy of satellite observations and model reanalyses about lower stratospheric temperature trends, two satellite-observed Microwave Sounding Unit (MSU) channel 4 (Ch 4) brightness temperature data and two GCM (ECMWF and GEOS) reanalyses during 1981${\sim}$1993 have been intercompared with the regression analysis of time series. The satellite data for the period of 1980${\sim}$1999 are MSU4 at nadir direction and SC4 at multiple scans, respectively, derived in this study and Spencer and Christy (1993). The MSU4 temperature over the globe during the above period shows the cooling trend of -0.35 K/decade, and the cooling over the global ocean is 1.2 times as much as that over the land. Lower stratospheric temperatures during the common period (1981${\sim}$1993) globally show the cooling in MSU4 (-0.14 K/decade), SC4 (-0.42 K/decade) and GEOS (-0.15 K/decade) which have strong annual cycles. However, ECMWF shows a little warming and weak annual cycle. The 95% confidence intervals of the lower stratospheric temperature trends are greater than those of midtropospheric (channel 2) trends, indicating less confidence in Ch 4. The lapse rate in the trend between the above two atmospheric layers is largest over the northern hemispheric land. MSU4 has low correlation with ECMWF over the globe, and high value with GEOS near the Korean peninsula. Lower correlations (r < 0.6) between MSU4 and SC4 (or ECMWF) occur over $30^{\circ}$N latitude belt, where subtropical jet stream passes. Temporal correlation among them over the globe is generally high (r > 0.6). Four kinds of lower stratospheric temperature data near the Korean peninsula commonly show cooling trends, of which the SC4 values (-0.82 K/decade) is the largest.