Depiction of the Trend and Variability of Pineapple Express Events by Seven Global Reanalysis Datasets
Location
ECC 216
Event Website
http://water.usu.edu/
Start Date
4-3-2012 11:20 AM
End Date
4-3-2012 11:40 AM
Description
We investigate the climatology and variability of the Pineapple Express (PE) events using a combination of seven global reanalyses. Extreme flooding events in the western United States have been attributed to PE conditions along the Pacific coast. Under the climate warming scenario, it is possible that increased tropical moisture will be transported towards North America through PE events. Because PE events are a large-scale phenomenon covering the vast Pacific Ocean, global reanalyses provide the best data coverage for the analysis of their climatology. We are interested in determining whether a change in the relative frequency, duration, and intensity of such events can be determined from the full records and different sources of reanalysis data. To determine the conditions leading to PE events, we create an index to isolate 10 “classic cases” that correspond to either literature or news coverage. The index for PE events is created by considering (1) The southerly and westerly components of column integrated water vapor flux (Q) at two locations, upstream and downstream of the precipitation region, (2) geopotential height at the 200 mb level in the Gulf of Alaska, and (3) precipitation amounts along the West Coast. A composite of synoptic conditions associated with these PE events are verified against the classic cases using three Reanalysis data sets (NCEP/NCAR Reanalysis I, NCEP/DOE Reanalysis II, NOAA-CIRES 20th Century Reanalysis V2 (20CR)), and the NCEP/CPC precipitation data. We run this PE index from October through April over 61 years (1950- 2010) for NCEP1, 59 years (1950-2008) for 20CR, and 32 years (1979-2010) for NCEP2. The selected cases used in the analysis agree well with each other. Throughout the 61 years, the frequency of PE events has not changed much and, all three reanalyses show a multi-decadal variability with a predominant frequency of 10-20 years. We will analyze PE events using four other reanalyses: (a) NCEP Climate Forecast System Reanalysis (CRSR), (b) NASA Modern Era Reanalysis for Research and Applications (MERRA), (c) ECMWF Reanalysis 40-year Project (ERA-40), (d) ECMWF Interim Reanalysis (ERA-Interim), and (e) Japanese 25-year Reanalysis (JRA-25). Intercomparison of the depiction of PE events by the various reanalyses will facilitate the assessment of uncertainty in any long-term changes of these events. A method to quantify the PE event intensity will also be developed and incorporated into this study. The intercomparison results of the synoptic property, trend, and climate variability of PE events will be presented in the conference.
Depiction of the Trend and Variability of Pineapple Express Events by Seven Global Reanalysis Datasets
ECC 216
We investigate the climatology and variability of the Pineapple Express (PE) events using a combination of seven global reanalyses. Extreme flooding events in the western United States have been attributed to PE conditions along the Pacific coast. Under the climate warming scenario, it is possible that increased tropical moisture will be transported towards North America through PE events. Because PE events are a large-scale phenomenon covering the vast Pacific Ocean, global reanalyses provide the best data coverage for the analysis of their climatology. We are interested in determining whether a change in the relative frequency, duration, and intensity of such events can be determined from the full records and different sources of reanalysis data. To determine the conditions leading to PE events, we create an index to isolate 10 “classic cases” that correspond to either literature or news coverage. The index for PE events is created by considering (1) The southerly and westerly components of column integrated water vapor flux (Q) at two locations, upstream and downstream of the precipitation region, (2) geopotential height at the 200 mb level in the Gulf of Alaska, and (3) precipitation amounts along the West Coast. A composite of synoptic conditions associated with these PE events are verified against the classic cases using three Reanalysis data sets (NCEP/NCAR Reanalysis I, NCEP/DOE Reanalysis II, NOAA-CIRES 20th Century Reanalysis V2 (20CR)), and the NCEP/CPC precipitation data. We run this PE index from October through April over 61 years (1950- 2010) for NCEP1, 59 years (1950-2008) for 20CR, and 32 years (1979-2010) for NCEP2. The selected cases used in the analysis agree well with each other. Throughout the 61 years, the frequency of PE events has not changed much and, all three reanalyses show a multi-decadal variability with a predominant frequency of 10-20 years. We will analyze PE events using four other reanalyses: (a) NCEP Climate Forecast System Reanalysis (CRSR), (b) NASA Modern Era Reanalysis for Research and Applications (MERRA), (c) ECMWF Reanalysis 40-year Project (ERA-40), (d) ECMWF Interim Reanalysis (ERA-Interim), and (e) Japanese 25-year Reanalysis (JRA-25). Intercomparison of the depiction of PE events by the various reanalyses will facilitate the assessment of uncertainty in any long-term changes of these events. A method to quantify the PE event intensity will also be developed and incorporated into this study. The intercomparison results of the synoptic property, trend, and climate variability of PE events will be presented in the conference.
https://digitalcommons.usu.edu/runoff/2012/AllAbstracts/5