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Potential benefit of extra radiosonde observations around the Chukchi Sea for the Alaskan short-range weather forecast

2018; Elsevier BV; Volume: 21; Linguagem: Inglês

10.1016/j.polar.2018.12.005

1876-4428

Minhee Lee, Joo‐Hong Kim, Hyo‐Jong Song, Jun Inoue, Kazutoshi Sato, A. Yamazaki,

Atmospheric and Environmental Gas Dynamics

In recent years, growing attentions have been paid to the potential benefit of extra observations over the data-sparse Arctic Ocean for weather forecasts. Here we also focus on such a case by targeting the inhabited land area, Alaska. During 2–18 August 2015, ship-borne radiosonde sounding observations were performed every 12 h (except 6-hourly from 12:00 UTC 11 August to 00:00 UTC 14 August) around the Chukchi Sea. To assess the impact of those extra radiosonde observations, two sets of ensemble forecast experiments (CTLf and OSE_Af) were produced, which were respectively initialized by atmospheric reanalysis data without (CTL) and with (OSE_A) additional assimilation of those data. The tropospheric circulation fields are compared to verify their differences in forecast performance. While two forecasts have similar performance in the earlier spin-up period of the analysis-forecast cycle (from 4 to 7 August), their performance tends to diverge in the later period (from 11 to 18 August) due to the accumulated influence on the error reduction in OSE_Af. Among the improved forecasts in OSE_Af, two most outperformed forecasts, each initialized on 00:00 UTC 12 and 00:00 UTC 14, show a notable improvement in predicting the developing trough over Alaska on 16–17 August by suppressing the development of erroneous high anomalies in CTLf. Though the positive impact of single-point observations is limited in a space, our results suggest that enhanced radiosonde profile observations in the data-sparse polar ocean could be beneficial for the forecasts beyond the observational area.