Homogeneity of the Temperature Data Series from ERA5 and MERRA2 and Temperature Trends

Abstract

The stratosphere and its dynamics are a very important part of atmospheric circulation. We need to analyze its climatology, as well as long-term trends. A long-term trend study needs homogenous datasets without significant artificial discontinuities. The analysis is based on the two newest released reanalyses, Modern Era-Retrospective Analysis (MERRA2) and European Center for Medium-Range Weather Forecast Reanalysis (ERA5). The aim of this study is to detect discontinuities in the temperature time series from the above reanalyses with the help of the Pettitt homogeneity test for pressure layers above 500 hPa up to 1 hPa in January and February, and show a comparison of temperature trends from the studied reanalyses and GPS radio occultation (GPS RO). We search for individual grid points where these discontinuities occur, and also for the years when they occur (geographical and temporal distribution). As expected, the study confirms better results for the Northern Hemisphere due to the denser data coverage. A high number of grid points with jumps on the Southern Hemisphere is found, especially at higher pressure levels (from 50 hPa). The spatial and vertical distribution of discontinuities is also presented. The vertical distribution reveals the reduction of the number of jumps around 10 hPa, especially for ERA5 reanalysis. The results show that ERA5 has significantly less jumps than MERRA2. We also study temperature trends from reanalyses and GPS RO and our analysis shows that the agreement between the reanalyses and observations are very good for the period 2006–2018.

How Well Does the ERA5 Reanalysis Capture the Extreme Climate Events Over China? Part II: Extreme Temperature

“…On the global scale, Poli et al (2016) compared the temperature data on the ERA-20C with the observation and demonstrated that the reanalysis data was 1K colder than the night observational data within 65 °north-south latitude. Kozubek et al (2020) indicated that the trend of temperature from ERA5 data has good consistency with observations data. Liu et al (2021) confirmed that the land surface temperature data on ERA5 products are highly consistent with the trend derived from satellite data in 2003-2017.…”

Climatology and Long-Term Trends in the Stratospheric Temperature and Wind Using ERA5

“…If we look at the trend comparison, the biggest differences can be found for 1 hPa, but for the lower pressure levels the main features are similar even when the amplitude is different. We also analyze a comparison of two reanalyses with GPS RO for the limited period 2010-2020, see [26]. From the comparison of two main reanalyses for a longer period and with GPS RO for a shorter period, we can say that at least down from 10 hPa ERA5 is suitable for our analysis.…”

Share of Discontinuities in the Ozone Concentration Data from Three Reanalyses

“…In each grid, all three tests estimate only one main discontinuity, so this procedure is not able to detect multiple discontinuities. The homogeneity tests used in this paper have been widely used in climatological research, particularly for precipitation and temperature analysis [17,18,[29][30][31][32], therefore, we assume their usability also for ozone studies. We are interested primarily in the share of grids with discontinuity to all grids.…”