As shown in the picture, "the near-surface weather situation map of a certain area in China at a certain time", look at the picture and answer the following questions. (1) The pressure value of isobar

As shown in the picture, "the near-surface weather situation map of a certain area in China at a certain time", look at the picture and answer the following questions. (1) The pressure value of isobar C in the figure is _ _ _ _ (greater than or equal to. The frontal surface (1) is located in the trough of low pressure, belonging to frontal cyclone. The central pressure is lower than the surrounding area, and the pressure value of isobar C is higher than D; The specific wind direction on the isobar chart is from high pressure to low pressure, and the northern hemisphere deflects to the right. At this time, the wind direction in Chongqing is northwest wind (or northerly wind).

(2) By the sign of the front, it can be judged that the front is a cold front, and there will be strong winds, cooling, rainfall and even snowfall when the cold front passes.

(3) Compared with Chongqing, Changsha has stronger wind, denser isobar and greater horizontal pressure gradient.

(4) The important role of rivers in the formation and development of Wuhan and Chongqing is to provide sufficient water sources and convenient water transportation.

(5) The reason why Reach A in the middle and lower reaches of the Yangtze River becomes an "overground river" is that it is located in the plain, with a curved channel, slow water flow, a large amount of sediment deposition, and the riverbed is constantly silted.

So the answer is:

(1) is higher than northwest wind (or northerly wind)

(2) Cold front, strong wind, cooling, rainfall and even snowfall.

(3) big? Dense isobar and large horizontal pressure gradient force?

(4) Provide sufficient water sources and water transport facilities.

(5) Located in the plain, the river channel is curved, the water flow is slow, a large amount of sediment is deposited, and the riverbed is continuously silted.