# A Study on Assimilation of CYGNSS Wind Speed Data for Tropical Convection during 2018 January MJO
## 3 Results
### Assimilation of the Combined Satellite Datasets
ASCAT (Figure 10d) observed the maximum wind speed of 28 m s\({}^{-1}\) with a small eye. CTRL (Figure 10e) underestimated TC Irving with a MSLP of 991 hPa and a maximum wind speed of 27 m s\({}^{-1}\). A better intensity and wind field was produced in DA_com (Figure 10f) with a MSLP of 982 hPa and a maximum surface wind speed of 32 m s\({}^{-1}\) and a smaller eye. From ASCAT, it seems that the strongest wind at this time appeared at the front right quadrant of TC Irving, and that there was no apparent wind asymmetry around the eyewall. In CTRL, the strongest wind was at the front to front left of TC Irving with a strong wind asymmetry. DA_com shows the strong wind occurring in both front left and front right quadrants. The asymmetry was not as apparent as the wind field in CTRL. Figure 10: Surface wind speed near TC Irving from (**a**) ASCAT observation at 0302 UTC, and surface wind speed prediction overplotted with sea level pressure from (**b**) CTRL, and (**c**) DA_com at 0300 UTC on 7 January 2018; and (**d**) ASCAT at 1436 UTC, and surface wind speed with sea level pressure from (**e**) CTRL, and (**f**) DA_com at 1500 UTC on 8 January 2018. Figure 11 shows the surface wind field for the WWB event around 1500 UTC on 7 January and 1600 UTC on 8 January 2018 when ASCAT captured a portion of the event. At both times, DA_com produced stronger wind field than CTRL. ASCAT (Figure 11a,d) shows wind speed \(>\) 8 m s\({}^{-1}\) over the area 65\({}^{\circ}\)-85\({}^{\circ}\)E and 10\({}^{\circ}\)S-0\({}^{\circ}\) with a maximum wind speed of 16 m s\({}^{-1}\). CTRL (Figure 11b,e) predicted much smaller areas that have wind speed \(>\) 8 m s\({}^{-1}\) with the maximum of 13 m s\({}^{-1}\). In comparison, DA_com (Figure 11c,f) produced large areas with wind speed over 8 m s\({}^{-1}\) and a maximum wind of 18 m s\({}^{-1}\). The location of the WWB was also better predicted in DA_com at 1600 UTC on 8 January 2018. Figure 12 compares the precipitation predictions from CTRL and DA_com with IMERG data at 1500 UTC on 7 January and 2100 UTC on 8 January 2018. At both times, DA_com a much stronger and better organized precipitation over the core region of TC Irving than CTRL. At 1500 UTC on 7 January, DA_com (Figure 12c) produced maximum rainfall of 36 mm h\({}^{-1}\) around the eyewall, which was pretty close to the observed 34 mm h\({}^{-1}\) by IMERG (Figure 12a), and 12 mm h\({}^{-1}\) higher than the one predicted in CTRL (Figure 12b). At 2100 UTC on 8 January 2018, both DA_com and CTRL underestimated the precipitation for TC Irving. IMERG (Figure 12d) estimated the maximum rainfall rate of 56 mm h\({}^{-1}\). CTRL (Figure 12e) predicted maximum rainfall of 20 mm h\({}^{-1}\). DA_com (Figure 12f) outperformed CTRL with a much stronger precipitation field with a maximum of 42 mm h\({}^{-1}\). Precipitation related to the WWB event was also better represented in DA_com (Figure 13). At 1200 UTC on 7 January 2018, IMERG observed strong convection with the maximum precipitation rate of 32 mm h\({}^{-1}\) at 75\({}^{\circ}\)-80\({}^{\circ}\)E and 5\({}^{\circ}\)-7\({}^{\circ}\)S. In CTRL, this storm was not predicted. With the assimilation of the combined datasets, DA_com produced heavy precipitation near the observed location with the maximum precipitation \(>\) 40 mm h\({}^{-1}\). A similar result was found at 2100 UTC on 8 January 2018. IMERG observed convection with maximum precipitation of 23 mm h\({}^{-1}\) at 67\({}^{\circ}\)-78\({}^{\circ}\)E and 4\({}^{\circ}\)-8\({}^{\circ}\)S. CTRL predicted multiple strong convective storms, but the locations were far from the observed one. DA_com was able to generate the precipitation at 70\({}^{\circ}\)-78\({}^{\circ}\)E and 4\({}^{\circ}\)-8\({}^{\circ}\)S with maximum precipitation of 26 mm h\({}^{-1}\).