DA_Team 3
Vertical Structure of Wind Field Differences
Comparison of ERA5 and JRA-55 wind speed and vector differences
across multiple pressure levels during Typhoon Hinnamnor.
This page examines vertical variations in wind field differences between ERA5 and JRA-55 during Typhoon Hinnamnor.
The difference is calculated as ERA5 minus JRA-55, so positive values indicate stronger winds in ERA5, while negative values indicate stronger winds in JRA-55. By comparing pressure levels from 200 hPa to 925 hPa, the analysis shows how the discrepancy between the two reanalysis datasets changes with altitude.
Each map shows ERA5 minus JRA-55 wind speed and vector differences at a specific pressure level.
The upper-level difference shows mixed positive and negative anomalies. JRA-55 tends to show stronger winds over the ocean east of the typhoon track, while ERA5 shows stronger winds along the northward track toward Japan and the Korean Peninsula. This suggests differences in the representation of upper-level outflow and jet-related flow.
1. Wind Difference Maps by Pressure Level
The overall pattern is similar to 200 hPa, but negative anomalies become more widespread over the ocean east of the typhoon track. This level shows one of the strongest upper-level differences, likely because 250 hPa is close to the jet-core layer where differences in AMV assimilation can be reflected more sensitively.
Positive and negative differences are more balanced
than at 200–250 hPa. Strong positive anomalies appear near the stagnation area northeast of Taiwan, indicating that ERA5 represents stronger winds in this part of the upper-level circulation during Hinnamnor’s slow-moving phase.
The difference pattern changes
from the upper-level structure.
Strong positive anomalies are concentrated near the stagnation area northeast of Taiwan, suggesting that ERA5 represents a stronger mid-level typhoon circulation than JRA-55 in this region.
Positive wind speed differences become more concentrated around the typhoon stagnation area. This indicates that the ERA5–JRA55 difference becomes increasingly connected to the storm’s inner circulation structure at lower pressure levels.
Broad positive anomalies dominate
across much of the domain.
ERA5 shows stronger lower-level winds along both the stagnation area and the northward track, suggesting a stronger representation of Hinnamnor’s primary circulation compared with JRA-55.
Positive differences remain dominant near the lower troposphere, although localized negative anomalies also appear near parts of the storm center. This suggests that boundary-layer processes and physical parameterization differences may affect the near-surface wind field in the two reanalysis datasets.
Upper Levels: 200–300 hPa
- Mixed positive and negative anomalies
- Complex pattern over East Asia and the western North Pacific
- Related to jet-level flow, outflow,
and steering flow
2. Vertical Trend Summary
Middle Levels: 500–700 hPa
- Positive anomalies concentrate near the stagnation area
- ERA5 shows stronger mid-level storm circulation
- Differences become more closely related to the typhoon track
Lower Levels: 850–925 hPa
- Broad positive differences dominate
- ERA5 shows stronger lower-tropospheric winds
- Local negative anomalies may reflect boundary-layer effects
Overall, the vertical comparison shows that ERA5 and JRA-55 differ not only in wind speed magnitude, but also in how the wind field changes with pressure level. At 200–300 hPa, the differences are spatially mixed and regionally dependent, suggesting sensitivity in the upper-level jet, outflow, and steering environment. From 500 hPa downward, positive differences become more organized around the typhoon stagnation area and circulation center. This indicates that ERA5 tends to represent stronger storm-related winds than JRA-55 in the middle and lower troposphere.