Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble
Abstract In the absence of convection permitting numerical weather prediction (NWP) ensembles, the most recent deterministic NWP precipitation forecast is usually addressed. However, the exact intensity, location and timing of a deterministic precipitation forecast is not always reliable because of...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2020-01-01
|
| Series: | Meteorological Applications |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/met.1840 |
| _version_ | 1828009991833911296 |
|---|---|
| author | Pavel Khain Yoav Levi Alon Shtivelman Elyakom Vadislavsky Evgeny Brainin Nir Stav |
| author_facet | Pavel Khain Yoav Levi Alon Shtivelman Elyakom Vadislavsky Evgeny Brainin Nir Stav |
| author_sort | Pavel Khain |
| collection | DOAJ |
| description | Abstract In the absence of convection permitting numerical weather prediction (NWP) ensembles, the most recent deterministic NWP precipitation forecast is usually addressed. However, the exact intensity, location and timing of a deterministic precipitation forecast is not always reliable because of the chaotic nature and complexity of precipitation formation mechanisms. This study examines a way to optimize the use of precipitation forecasts for deterministic NWP models. More specifically, it suggests using a spatially smoothed time‐lagged ensemble (TLE) to obtain more reliable precipitation forecasts. A global NWP model (integrated forecast system—IFS) and a regional convection permitting NWP model (COSMO) over the Eastern Mediterranean during the period 2016–2018 were used for the analysis. First, the paper defines light, light–moderate and moderate intensities for 6 hr accumulated precipitation (6hAP) and investigates the corresponding definitions for 1 hr accumulated precipitation (1hAP). Next, fractional skill score (FSS) are used to estimate the optimal spatial smoothing scale of a deterministic precipitation forecast for the three intensity categories for the 6hAP and 1hAP. The FSS is also used to compare COSMO and IFS deterministic precipitation forecasts, and to analyse the skill degradation with the forecast range. It is quantitatively shown that the useful scale of precipitation forecasts is smaller for larger accumulation time intervals. Finally, precipitation forecasts for TLE are formed from successive smoothed deterministic forecasts and compared with the most recent deterministic forecast. It is found that, on average, TLEs have better skills for both 6hAP and 1hAP. The reason for this improvement in skill is illustrated using a case study as an example. |
| first_indexed | 2024-04-10T08:47:13Z |
| format | Article |
| id | doaj.art-b48900770c99431b86c00488dce2b160 |
| institution | Directory Open Access Journal |
| issn | 1350-4827 1469-8080 |
| language | English |
| last_indexed | 2024-04-10T08:47:13Z |
| publishDate | 2020-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Meteorological Applications |
| spelling | doaj.art-b48900770c99431b86c00488dce2b1602023-02-22T07:11:32ZengWileyMeteorological Applications1350-48271469-80802020-01-01271n/an/a10.1002/met.1840Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemblePavel Khain0Yoav Levi1Alon Shtivelman2Elyakom Vadislavsky3Evgeny Brainin4Nir Stav5The Israel Meteorological Service Bet‐Dagan, IsraelThe Israel Meteorological Service Bet‐Dagan, IsraelThe Israel Meteorological Service Bet‐Dagan, IsraelThe Israel Meteorological Service Bet‐Dagan, IsraelThe Israel Meteorological Service Bet‐Dagan, IsraelThe Israel Meteorological Service Bet‐Dagan, IsraelAbstract In the absence of convection permitting numerical weather prediction (NWP) ensembles, the most recent deterministic NWP precipitation forecast is usually addressed. However, the exact intensity, location and timing of a deterministic precipitation forecast is not always reliable because of the chaotic nature and complexity of precipitation formation mechanisms. This study examines a way to optimize the use of precipitation forecasts for deterministic NWP models. More specifically, it suggests using a spatially smoothed time‐lagged ensemble (TLE) to obtain more reliable precipitation forecasts. A global NWP model (integrated forecast system—IFS) and a regional convection permitting NWP model (COSMO) over the Eastern Mediterranean during the period 2016–2018 were used for the analysis. First, the paper defines light, light–moderate and moderate intensities for 6 hr accumulated precipitation (6hAP) and investigates the corresponding definitions for 1 hr accumulated precipitation (1hAP). Next, fractional skill score (FSS) are used to estimate the optimal spatial smoothing scale of a deterministic precipitation forecast for the three intensity categories for the 6hAP and 1hAP. The FSS is also used to compare COSMO and IFS deterministic precipitation forecasts, and to analyse the skill degradation with the forecast range. It is quantitatively shown that the useful scale of precipitation forecasts is smaller for larger accumulation time intervals. Finally, precipitation forecasts for TLE are formed from successive smoothed deterministic forecasts and compared with the most recent deterministic forecast. It is found that, on average, TLEs have better skills for both 6hAP and 1hAP. The reason for this improvement in skill is illustrated using a case study as an example.https://doi.org/10.1002/met.1840convection permitting modelsfractional skill score (FSS)numerical weather prediction (NWP)precipitation forecasttime‐lagged ensemble |
| spellingShingle | Pavel Khain Yoav Levi Alon Shtivelman Elyakom Vadislavsky Evgeny Brainin Nir Stav Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble Meteorological Applications convection permitting models fractional skill score (FSS) numerical weather prediction (NWP) precipitation forecast time‐lagged ensemble |
| title | Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble |
| title_full | Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble |
| title_fullStr | Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble |
| title_full_unstemmed | Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble |
| title_short | Improving the precipitation forecast over the Eastern Mediterranean using a smoothed time‐lagged ensemble |
| title_sort | improving the precipitation forecast over the eastern mediterranean using a smoothed time lagged ensemble |
| topic | convection permitting models fractional skill score (FSS) numerical weather prediction (NWP) precipitation forecast time‐lagged ensemble |
| url | https://doi.org/10.1002/met.1840 |
| work_keys_str_mv | AT pavelkhain improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble AT yoavlevi improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble AT alonshtivelman improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble AT elyakomvadislavsky improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble AT evgenybrainin improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble AT nirstav improvingtheprecipitationforecastovertheeasternmediterraneanusingasmoothedtimelaggedensemble |