AEROGRAPHER'S MATE 3 & 2 



land station observations are not entered aboard 

 ships. For more details, see FMH No. 1. 



STATION PRESSURE (COL. 23).— Station pres- 

 sure aboard ship is determined from precision 

 aneroid barometers. It is entered in the same 

 manner as in column 17 on MF1-10. 



When rolling of the ship causes the indicator 

 on the aneroid barometer to oscillate, the mean 

 position is used for the station pressure. 



SUMMARY OF THE DAY (COL. 57).— Enter 

 the lowest pressure recorded in the 24-hour period 

 in millibars and tenths. 



Barometer Comparisons, 

 MF1-13 



To ensure that proper and correct pressure 

 data is being computed, especially with respect 

 to altimeter settings, the aneroid barometer will 

 be routinely compared with the mercurial barom- 

 eter to determine that suitable corrections are 

 being applied to the aneroid barometer. 



Once installed and operationally accepted as 

 a reliable barometer, each weather office should 

 make two comparisons, at 6-hourly intervals on 

 the same day of each week. These read- 

 ings should be entered on MF1-13, in 

 accordance with the instructions printed on the 

 back of the form. For further information on 

 the comparisons and use of the computed com- 

 parisons in relation to the unreliable performance 

 of an aneroid barometer, refer to FMH-1, chapter 

 A12. 



Barograms 



Microbarograph charts should be handled in 

 the following manner: 



1. Before placing a chart on the barograph, 

 use a typewriter, rubber stamp, or pen and ink 

 to enter the following data: 



a, In the spaces provided, enter the 

 name of the station and its type (NAS, FWC, 

 etc.), state, meridian of local standard time (15th, 

 90th, etc.), and elevation of the station (Hp) to 

 the nearest foot. Where provision is not made for 

 the H p entry, identify the value with the prefix 

 Hp =. Aboard ship, enter the name of the ship 

 and route "from - to." 



b. In the spaces provided, or above the 

 appropriate noontime lines, enter the date of 

 beginning and ending of the trace. 



c. Immediately preceding the printed 

 figures along the first and last time arcs, enter 

 the appropriate figures to indicate the chart range 

 (e.g., 28 preceding the printed 00 on the 28.00 

 inch line). 



d. In the spaces provided, or near the 

 point where trace will begin, enter "ON:" and 

 the time to the nearest minute (LST at shore 

 stations; GMT aboard ship) and the current 

 station pressure. 



2. After adjustments or removal of a com- 

 pleted microbarograph chart, use the following 

 procedure: 



a. Enter the time of each adjustment, 

 and an arrow to indicate the point of adjustment. 



b. In the spaces provided, or near the 

 end of the trace, enter "OFF:" and the time 

 to the nearest minute and the current station 

 pressure. 



c. Enter the appropriate corrections 

 above the time-check lines. The pen of the marine 

 barograph should be touched lightly once each 

 day at the 1200 GMT observation, and the 

 correction to the marine barograph reading deter- 

 mined by comparing the corrected aneroid barom- 

 eter reading with the microbarograph reading. 

 These corrections are entered at the corre- 

 sponding points on the barogram after the latter 

 has been removed from the cylinder. In addition, 

 aboard ship, the position is entered each day 

 beside the 1200 GMT time-check. 



d. When adjustment for pressure is 

 made, enter the current station pressure and 

 corrections applying to both the preceding and 

 following record (i.e., -.055/0) near the break 

 in the trace. 



3. Change charts at 6-hourly times (0000, 

 0600 GMT, etc.) closest to noon LST on the 

 1st, 5th, 9th, etc., day of the month. 



4. Microbarograph charts are forwarded to 

 Naval Weather Service Detachment, Ashevllle, 

 N.C., in accordance with procedures listed in 

 chapter 11 of this training manual. 



BAROGRAPHS 



OPEN-SCALE 

 BAROGRAPH (ML-3) 



The open- scale barograph (ML-3) is often 

 referred to as the microbarograph, just as the 

 marine barograph is. This instrument has been 



20 



