Investigating long-term trends in noctilucent clouds observed with European Nadir-Viewing satellite instruments

研究欧洲天底观测卫星仪器观测到的夜光云的长期趋势

基本信息

批准号：
255787981
负责人：
Professor Dr. Christian von Savigny, Ph.D.
金额：
--
依托单位：
Institut für Physik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/255787981?language=en
关键词：
Investigating long term trends noctilucent

项目摘要

Noctilucent clouds (NLCs) or polar mesospheric clouds (PMCs) are optically thin water-ice clouds occurring near the polar summer mesopause at latitudes exceeding about 50 deg and altitudes of 82 - 85 km. NLCs were intensively studied in the past two decades, because of their role as potential indicators of global change. Long-term satellite observations of NLCs using the BUV, SBUV and SBUV/2 instruments on Nimbus-7 and the NOAA satellite series in fact show evidence for a long-term increase in NLC albedo (DeLand et al., 2007) and NLC occurrence frequency (Shettle et al., 2009) - apart from a pronounced 11-year solar cycle signature. This long-term trend was recently questioned by a study by Stevens et al. (2007), who investigated long-term trends in NLC albedo and ice mass using part of the BUV/SBUV/2 data set limited to a fixed local time. Astonishingly, the selection of this subset led to the disappearance of the long-term trends in NLC reported earlier. These results suggest that the changing local time coverage associated with the drifting orbits of the satellites hosting the SBUV/2 instruments may spuriously introduce the long-term trends in SBUV/2 NLC observations. This issue is still unresolved, despite its great importance in terms of our scientific understanding of climate change in the upper mesospheric region of the Earth's atmosphere.The main purpose of this study is to address this discrepancy in NLC analyses of the SBUV/2 observations using satellite observations with the European nadir-viewing instruments GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) and GOME-2. Nadir observations with these instruments are uniquely suited to investigate the issue discussed above, because the satellites hosting these instruments (ERS-2 (GOME), Envisat (SCIAMACHY), and MetOp-A (GOME-2)) orbit the Earth in sun-synchronous orbits with fixed descending nodes, i.e. equator-crossing local solar times. This is a great advantage compared to the NOAA satellites hosting the SBUV/2 instruments, and implies that possible long-term trends in the derived NLC parameters will not be affected by local time drifts.Because the GOME and SCIAMACHY Nadir observations were not yet used for NLC retrievals an NLC retrieval algorithm will be implemented and will be applied to the entire GOME and SCIAMACHY data sets as part of the research proposed here. By the end of the proposed project a 20-year data set - covering almost 2 solar cycles - of data sets of NLC albedo, occurrence rate and ice mass will be available from the European Nadir UV sounders. The derived NLC data products will be used to quantify solar cycle (both at the 11-year and the 27-day time scale) and long-term variations in NLC parameters, and to address the issue, whether the long-term trend in SBUV/2 NLC time series is affected by slow changes in the local time sampling associated with drifting orbits.

夜光云（NLC）或极地层云（PMC）是光学上的薄冰云，发生在极性夏季间层附近，纬度高约50度，高度为82-85 km。在过去的二十年中，NLC被深入研究，因为它们是全球变化的潜在指标。 Long-term satellite observations of NLCs using the BUV, SBUV and SBUV/2 instruments on Nimbus-7 and the NOAA satellite series in fact show evidence for a long-term increase in NLC albedo (DeLand et al., 2007) and NLC occurrence frequency (Shettle et al., 2009) - apart from a pronounced 11-year solar cycle signature.史蒂文斯（Stevens）等人的一项研究最近对这种长期趋势进行了质疑。（2007年），他使用BUV/SBUV/2数据集的一部分限制在固定的当地时间，研究了NLC反照率和冰量的长期趋势。令人惊讶的是，该子集的选择导致NLC早期报道的长期趋势的消失。这些结果表明，与托管SBUV/2仪器的卫星漂流轨道相关的当地时间覆盖率变化可能会假冒sbuv/2 NLC观察的长期趋势。 This issue is still unresolved, despite its great importance in terms of our scientific understanding of climate change in the upper mesospheric region of the Earth's atmosphere.The main purpose of this study is to address this discrepancy in NLC analyses of the SBUV/2 observations using satellite observations with the European nadir-viewing instruments GOME (Global Ozone Monitoring Experiment), SCIAMACHY (SCanning Imaging Absorption用于大气图表学的光谱仪和GOME-2。 Nadir observations with these instruments are uniquely suited to investigate the issue discussed above, because the satellites hosting these instruments (ERS-2 (GOME), Envisat (SCIAMACHY), and MetOp-A (GOME-2)) orbit the Earth in sun-synchronous orbits with fixed descending nodes, i.e. equator-crossing local solar times. This is a great advantage compared to the NOAA satellites hosting the SBUV/2 instruments, and implies that possible long-term trends in the derived NLC parameters will not be affected by local time drifts.Because the GOME and SCIAMACHY Nadir observations were not yet used for NLC retrievals an NLC retrieval algorithm will be implemented and will be applied to the entire GOME and SCIAMACHY data sets as part在这里提出的研究。到拟议项目结束时，NLC反照率，发生率和冰质量的数据集涵盖了20年的数据集，涵盖了近2个太阳能周期。派生的NLC数据产品将用于量化太阳周期（在11年和27天的时间尺度上）和NLC参数的长期变化，并解决问题，是否会受到SBUV/2 NLC时间序列的长期趋势是否受到与Drififting Orbits相关的局部时间采样的慢变化的影响。