Self Assessment 10

§ 37 – 39



128. Of the subjects connected with weather experienced at sea:

‘Meteorology’ is the science of the atmosphere, embracing both weather and climate

129. Which of the following components of the atmosphere affect the weather:

water vapour

130. The level at which temperature stops falling with increase in height is called

the tropopause

131. The average atmospheric pressure at sea level is:

1015 millibars

132. Atmospheric pressure can be measured with:

a mercurial barometer – an aneroid barometer

133. Lines on a weather map joining places of equal atmospheric pressure are:


134. Enclosed areas of low pressure are known as:

a Depression

135. Enclosed area of high pressure are known as:

an Anticyclone

136. An outward extension from a High is called:

a Ridge – a Wedge

137. An outward extension from a Low is called:

a Trough

138. The horizontal movement of air called wind is caused by:

differences in the temperature of the air – differences in atmospheric pressure – cooler air flowing in under rising warm air

139. Air tends to flow:

from High to Low pressure areas almost parallel to the isobars

140. In the northern hemisphere winds circulate:

clockwise round an area of high pressure – anti-clockwise round an area of low pressure

141. The closer isobars are together on a weather map:

the stronger the wind will be

142. The actual surface wind is less than the geostrophic wind because:

of the frictional effect of the Earth’s surface

143. True wind speed on a vessel at sea should be:

estimated using the Beaufort hind Scale

144. Wind direction is always quoted as the direction:

from which it blows

145. When the direction of the wind changes in a clockwise direction:

the wind is said to veer

146. The capacity of the air for holding water vapour is important because:

without it day temperatures would be much colder than they are – warm air is capable of holding considerably more water than cold air – without it there would be neither clouds nor rain

147. A measure of the amount of water vapour present in the air is called:

the humidity

148. The temperature to which air must be cooled in order to release water is called:

the dew point

149. Clouds mist and fog are formed by the condensation of water vapour on:

salt particles in the atmosphere – minute particles in the air which are products of combustion – particles of sea spray

150. The dispersal of cloud can be brought about by:

a rise in temperature resulting in evaporation – precipitation (rain, hail or snow)

151. Situations likely to give rise to fog at sea are:

air moving from warm land on to a cold sea surface – air moving from warm sea on to a cold sea current

152. Weather to be expected in a Tropical Maritime air mass includes:

high relative humidity and tendency for sea fog

153. Weather to be expected in a Polar Maritime air mass includes:

wind between SW and N and gusting

154. A cold front is an area:

where cold air undercuts warm air and forces it upwards

155. The Polar Front is:

156. a quasi—stationary front in the North Atlantic.

157. Weather in the warm sector of a depression is usually:

temperature and humidity high – overcast with low stratus and intermittent or continuous drizzle

158. Characteristics of a developing High or Anticyclone are:

widespread slow descent of air know as subsidence

159. The Meteorological Office ‘Shipping Forecast is broadcast in full daily:

by BBC Radio 4 on 1500 metres (200 kHz)

160. Other useful sources of weather data for mariners are:

weather maps issued by regional weather centres

161. The term “soon” in a weather forecast means:

within 6-12 hours

162. The term “intense” in a weather forecast means:

a depression with a steep pressure gradient (isobars close together) – an anti-cyclone with very high pressure at the centre

163. Visibility is said to be “poor” when:

an object is clearly recognisable at between 1 to 2 miles



164. Radio-sonde equipment as used by meteorologists is:

temperature, humidity and pressure measuring devices carried into the upper air by balloon

165.  Sferic equipment is used by meteorologists:

to fix the position of thunderstorms by detecting the electromagnetic waves they emit

166. Weather satellites orbit outside the Earth‘s atmosphere and are used to:

photograph whole cloud systems of depressions with associated fronts – measure and transmit data on heat radiations from earth, sea, clouds, etc

167. Temperature may be described as:

the degree of hotness or coldness of a substance

168. Electromagnetic radiation is:

the transfer of heat between two bodies which are not in contact

169. The difference between day and night temperatures over the sea is much less than

over the land because:

solar radiation penetrates to greater depths in the sea

170. The air temperature at sea should be measured:

in the shade on the windward side of the vessel

171. The sea temperature should be measured:

with a special sheathed thermometer fitted with a sea-water reservoir – using a sample of water taken near the sea surface – only after bringing the temperature of thermometer and bucket approximately to the temperature of the sea surface

172. The increase of air temperature with height in the troposphere is called:

the negative lapse rate – an inversion

173. Dry air is said to be stable when:

its lapse rate is less than the dry adiabatic lapse rate

174. The ideal place to stow an aneroid barometer in a small craft is:

in a box in the cockpit

175. The average atmospheric pressure is:

1013 mb

176. The best indication of true wind direction and speed is given by:

the direction and state of the sea surface waves

177. The size of sea waves is determined by:

the length at time the wind has been blowing in the same direction – the distance upwind over which the wind is able to act from the same direction

178. ‘Swell’ is a wave disturbance or system which:

is generated by past wind at a distance



179. Briefly explain each of the following: –

a. Diurnal range of barometric pressure

b. Article 35 of the International Convention for the Safety of Life at Sea.

c. The Horse Latitudes

d. Inter-tropical Convergence Zone,

180. Discuss the nature, location, directions and strengths of the Trade Winds and the general weather experienced in these areas.

181. What is the cause of the SW Monsoon of the North Indian Ocean, China Sea and Western North Pacific, when does this seasonal wind occur and how does it affect the climate of these areas?

182. What is a Tropical Revolving Storm?

183. By what other names, and in what areas are T.R.S. known?

184. Draw a plan diagram of a T.R.S., indicating average barometric pressure and wind strengths and showing a scale of nautical miles.

185. With respect to a T.R.S., explain the meaning of the following: –

a. Vortex

b. Vertex 

c. Storm Field

d. Storm Tide.

186. Draw two diagrams, each showing the characteristic path of a T.R.S. (with alternatives), in: 

a. The Northern Hemisphere

b. The Southern Hemisphere.

187. In a small craft making an ocean passage what signs would give the approach of a T.R.S. and what action would you take?

188. What precautions would you take against the dangers of a T.R.S: –

a. at the point of re-curvature?

b. in harbour?

189. Describe the three types of Current Chart which are available stating how each could be used by an ocean navigator.

190. Explain the cause of: –

a. a drift current

b. a gradient current

191. Name and describe the locations of three examples of each type of current in the ocean circulations of the world.

192. Describe the winds, weather and ocean currents likely to be experienced on a round-the-world voyage from the U.K. via Cape Town (South Africa), Sydney Australia), Cape Horn (South America), Rio de Janeiro (Brazil), Barbados-(W. Indies) and Bermuda.

193. Are any Tropical Revolving Storms likely to be experienced on passage in 195. above;  If so, where, and at what time of the year should these areas be avoided?

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