Ellis Remsberg

This work is a diagnostic study of distributions of tropical tropospheric column ozone (TRCO) based on subtracting Limb Infrared Monitor of the Stratosphere (LIMS) Version 6 (V6) Level 3 stratospheric column ozone (SCO) values from Total Ozone Mapping Spectrometer (TOMS) total ozone for several selected days of 1978–1979. The focus of this study is the low latitudes, where the tropopause is near 100 hPa and zonal wave activity is weak. TRCO exhibits a zonal wave-1 feature in the southern tropics with maximum values near 0° longitude during November 1978. Its zonal variation is 70 to 30 Dobson units (DU) and agrees with that of other similar analysis studies. V6 estimates of SCO and calculated TRCO are less reliable in March and May 1979 because those data are affected by temperature biases of order -1.0 to -2.0 K at 30 and 50 hPa; retrieved ozone at those levels may be too large by ~20 % as a result. The LIMS Level 3 sequential estimation algorithm provides smoothed zonal wave ozone amplitudes and reduced zonal variations of SCO. The corresponding calculated TRCO amplitudes are enhanced and not quantitative in those instances. The findings herein should be helpful to others, as they analyze infrared limb measurements of ozone and subtract their stratospheric column amounts from coincident total ozone to obtain accurate zonal variations of tropospheric ozone.

This work is a diagnostic study of distributions of tropical tropospheric column ozone (TRCO) based on subtracting Limb Infrared Monitor of the Stratosphere (LIMS) Version 6 (V6) Level 3 stratospheric column ozone (SCO) values from Total Ozone Mapping Spectrometer (TOMS) total ozone for several selected days of 1978–1979. The focus of this study is the low latitudes, where the tropopause is near 100 hPa and zonal wave activity is weak. TRCO exhibits a zonal wave-1 feature in the southern tropics with maximum values near 0° longitude during November 1978. Its zonal variation is 70 to 30 Dobson units (DU) and agrees with that of other similar analysis studies. V6 estimates of SCO and calculated TRCO are less reliable in March and May 1979 because those data are affected by temperature biases of order -1.0 to -2.0 K at 30 and 50 hPa; retrieved ozone at those levels may be too large by ~20 % as a result. The LIMS Level 3 sequential estimation algorithm provides smoothed zonal wave ozone amplitudes and reduced zonal variations of SCO. The corresponding calculated TRCO amplitudes are enhanced and not quantitative in those instances. The findings herein should be helpful to others, as they analyze infrared limb measurements of ozone and subtract their stratospheric column amounts from coincident total ozone to obtain accurate zonal variations of tropospheric ozone.

This work is a diagnostic study of distributions of tropical tropospheric column ozone (TRCO) based on subtracting Limb Infrared Monitor of the Stratosphere (LIMS) Version 6 (V6) Level 3 stratospheric column ozone (SCO) values from Total Ozone Mapping Spectrometer (TOMS) total ozone for several selected days of 1978–1979. The focus of this study is the low latitudes, where the tropopause is near 100 hPa and zonal wave activity is weak. TRCO exhibits a zonal wave-1 feature in the southern tropics with maximum values near 0° longitude during November 1978. Its zonal variation is 70 to 30 Dobson units (DU) and agrees with that of other similar analysis studies. V6 estimates of SCO and calculated TRCO are less reliable in March and May 1979 because those data are affected by temperature biases of order -1.0 to -2.0 K at 30 and 50 hPa; retrieved ozone at those levels may be too large by ~20 % as a result. The LIMS Level 3 sequential estimation algorithm provides smoothed zonal wave ozone amplitudes and reduced zonal variations of SCO. The corresponding calculated TRCO amplitudes are enhanced and not quantitative in those instances. The findings herein should be helpful to others, as they analyze infrared limb measurements of ozone and subtract their stratospheric column amounts from coincident total ozone to obtain accurate zonal variations of tropospheric ozone.

This work is a diagnostic study of distributions of tropical tropospheric column ozone (TRCO) based on subtracting Limb Infrared Monitor of the Stratosphere (LIMS) Version 6 (V6) Level 3 stratospheric column ozone (SCO) values from Total Ozone Mapping Spectrometer (TOMS) total ozone for several selected days of 1978–1979. The focus of this study is the low latitudes, where the tropopause is near 100 hPa and zonal wave activity is weak. TRCO exhibits a zonal wave-1 feature in the southern tropics with maximum values near 0° longitude during November 1978. Its zonal variation is 70 to 30 Dobson units (DU) and agrees with that of other similar analysis studies. V6 estimates of SCO and calculated TRCO are less reliable in March and May 1979 because those data are affected by temperature biases of order -1.0 to -2.0 K at 30 and 50 hPa; retrieved ozone at those levels may be too large by ~20 % as a result. The LIMS Level 3 sequential estimation algorithm provides smoothed zonal wave ozone amplitudes and reduced zonal variations of SCO. The corresponding calculated TRCO amplitudes are enhanced and not quantitative in those instances. The findings herein should be helpful to others, as they analyze infrared limb measurements of ozone and subtract their stratospheric column amounts from coincident total ozone to obtain accurate zonal variations of tropospheric ozone.

This study makes use of Halogen Occultation Experiment (HALOE) methane (CH₄) in a search for multi-year changes in the Brewer–Dobson circulation (BDC). Changes in CH₄ are determined for three successive 5-year time spans from 1992 to 2005, and there are significant differences between them. There is a clear separation between the changes in the Northern Hemisphere near 30 hPa and at the transition of the shallow and deep branches of the BDC. The CH₄ changes are positive and large in the shallow branch following the eruption of Pinatubo, but they then decrease and agree with tropospheric trends in the late 1990s and early 2000s. CH₄ decreases in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH₄ continues to decrease in the deep branch in the late 1990s but then increases in the early 2000s, although those changes are small compared with the seasonal and interannual variations of CH₄. Multi-year changes are due, in part, to wave forcings during the El Niño–Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH₄ provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.

This study makes use of Halogen Occultation Experiment (HALOE) methane (CH₄) in a search for multi-year changes in the Brewer-Dobson Circulation (BDC). Changes in CH₄ are determined for three, successive 5-yr time spans from 1992 to 2005, and there are significant differences in them. There is a clear separation for the changes in the northern hemisphere near 30 hPa or at the transition of the shallow and deep branches of the BDC. The CH₄ changes were positive and large in the shallow branch following the eruption of Pinatubo, but they then decreased and agreed with tropospheric trends in the late 1990s and early 2000s. CH₄ decreased in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH₄ continued to decrease in the deep branch in the late 1990s but then increased in the early 2000s, although the changes were small compared with the seasonal and interannual variations of CH₄. Those multi-year changes were due, in part, to wave forcings during El Nino Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH₄ provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.

This study makes use of Halogen Occultation Experiment (HALOE) methane (CH₄) in a search for multi-year changes in the Brewer-Dobson Circulation (BDC). Changes in CH₄ are determined for three, successive 5-yr time spans from 1992 to 2005, and there are significant differences in them. There is a clear separation for the changes in the northern hemisphere near 30 hPa or at the transition of the shallow and deep branches of the BDC. The CH₄ changes were positive and large in the shallow branch following the eruption of Pinatubo, but they then decreased and agreed with tropospheric trends in the late 1990s and early 2000s. CH₄ decreased in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH₄ continued to decrease in the deep branch in the late 1990s but then increased in the early 2000s, although the changes were small compared with the seasonal and interannual variations of CH₄. Those multi-year changes were due, in part, to wave forcings during El Nino Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH₄ provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.

This study makes use of Halogen Occultation Experiment (HALOE) methane (CH₄) in a search for multi-year changes in the Brewer-Dobson Circulation (BDC). Changes in CH₄ are determined for three, successive 5-yr time spans from 1992 to 2005, and there are significant differences in them. There is a clear separation for the changes in the northern hemisphere near 30 hPa or at the transition of the shallow and deep branches of the BDC. The CH₄ changes were positive and large in the shallow branch following the eruption of Pinatubo, but they then decreased and agreed with tropospheric trends in the late 1990s and early 2000s. CH₄ decreased in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH₄ continued to decrease in the deep branch in the late 1990s but then increased in the early 2000s, although the changes were small compared with the seasonal and interannual variations of CH₄. Those multi-year changes were due, in part, to wave forcings during El Nino Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH₄ provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.

This study makes use of Halogen Occultation Experiment (HALOE) methane (CH₄) in a search for multi-year changes in the Brewer-Dobson Circulation (BDC). Changes in CH₄ are determined for three, successive 5-yr time spans from 1992 to 2005, and there are significant differences in them. There is a clear separation for the changes in the northern hemisphere near 30 hPa or at the transition of the shallow and deep branches of the BDC. The CH₄ changes were positive and large in the shallow branch following the eruption of Pinatubo, but they then decreased and agreed with tropospheric trends in the late 1990s and early 2000s. CH₄ decreased in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH₄ continued to decrease in the deep branch in the late 1990s but then increased in the early 2000s, although the changes were small compared with the seasonal and interannual variations of CH₄. Those multi-year changes were due, in part, to wave forcings during El Nino Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH₄ provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.