Hadley cell dynamics in Japanese Reanalysis-55 dataset: evaluation using other reanalysis datasets and global radiosonde network observations

Significant Role of Orography in Shaping the Northern Hadley Circulation and Its Poleward Expansion During Boreal Summer

“…Figure displays the NH HC in July 1993 based on four reanalyses derived from the traditional (first row), TPDGAC (second row), and local partitioning (third row) methods without considering the surface pressure. Similar to the results of Mathew et al (), Figure d (see also Figure 7b in Mathew et al, ) shows that the sinking branch of the NH HC based on the traditional method derived from the JRA‐55 data set extends to approximately 42.5°N in July 1993, and a southward circulation (i.e., the minor circulation) is embedded within the conventional northward circulation. However, Figure S1j shows that there are four zones with a MSF of zero at 500 hPa because of the presence of the minor circulation.…”

“…The NH HC in July 1993 is studied in this section for better comparison with the results in Mathew et al (), and the main result does not change if other year and month (i.e., June to September during 1979–2016) are used. Figure displays the NH HC in July 1993 based on four reanalyses derived from the traditional (first row), TPDGAC (second row), and local partitioning (third row) methods without considering the surface pressure.…”

“…The traditionally defined HC, which has an ascending branch near the equator and sinking branches in the subtropics, accompanied by the two thermally driven circulations caused by the Tibetan Plateau, manifests the shape of HC shown in Figure 7b in Mathew et al (). To verify the description proposed above, Mathew et al () excluded the influence of the Tibetan Plateau by removing the region (50°E–120°E) when calculating the MSF and noted that the minor circulation disappears during boreal summer (Figure S2d), suggesting that the Tibetan Plateau may have a vital influence on the presence of the minor circulation.…”

“…In a recent study, Mathew et al () claimed that a minor circulation can be observed in the Northern Hemisphere (NH) HC during boreal summer (June to September) in some years, especially in June and July (e.g., Figure 7b in Mathew et al, ; see also Figure d). Since the sinking branch of the HC is commonly defined as the first latitude poleward of the circulation center with a MSF of zero at 500 hPa, Mathew et al () pointed out that using this definition could lead to a miscalculation of the location of the sinking branch of the HC in some years because of the presence of the minor circulation in these HCs (e.g., Figure 7c in Mathew et al, ; see also Figure S1j). Mathew et al () also indicated that the Tibetan Plateau seems to be the key to the presence of the minor circulation.…”

“…Since the sinking branch of the HC is commonly defined as the first latitude poleward of the circulation center with a MSF of zero at 500 hPa, Mathew et al () pointed out that using this definition could lead to a miscalculation of the location of the sinking branch of the HC in some years because of the presence of the minor circulation in these HCs (e.g., Figure 7c in Mathew et al, ; see also Figure S1j). Mathew et al () also indicated that the Tibetan Plateau seems to be the key to the presence of the minor circulation. The thermal effects of the Tibetan Plateau at middle latitudes during boreal summer include a maximum temperature center at approximately 35°N, which leads to thermally driven circulations with ascending motion at approximately 35°N and sinking motions at 25°N and 42.5°N.…”